Vibrating gyrosensor

ABSTRACT

A vibrating gyrosensor includes a support substrate on which a wiring pattern having a plurality of lands is formed, and vibrating elements mounted on a surface of the support substrate, wherein at least two vibrating elements are mounted on the support substrate, for detecting vibrations in different axial directions.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese PatentApplication JP 2005-106718 filed in the Japanese Patent Office on Mar.4, 2005, Japanese Patent Application JP 2005-063075 filed in theJapanese Patent Office on Mar. 7, 2005, Japanese Patent Application JP2005-190234 filed in the Japanese Patent Office on Jun. 29, 2005, andJapanese Patent Application JP 2005-374326 filed in the Japanese PatentOffice on Dec. 27, 2005, the entire contents of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an angular velocity sensor used, forexample, for detecting motion blurring of a video camera, detecting amotion in a virtual reality device, detecting a direction in a carnavigation system, and the like. Specifically, the invention relates toa vibrating gyrosensor including a vibrating element having a cantilevervibrator.

2. Description of the Related Art

As consumer angular velocity sensors, so-called vibrating gyrosensorsare widely used, in each which a cantilever vibrator is vibrated at apredetermined resonance frequency, and Coriolis' force produced by theinfluence of an angular velocity is detected by a piezoelectric elementto detect the angular velocity.

Vibrating gyrosensors have the advantages of a simple mechanism, a shortstarting time, and a low manufacturing cost. For example, vibratinggyrosensors are mounted on electronic devices, such as a video camera, avirtual reality device, and a car navigation system and used as sensorsfor detecting motion burring, a motion, and a direction, respectively.

A usual vibrating gyrosensor includes a vibrating element which ismanufactured by machine-cutting an appropriate piezoelectric material toform a predetermined shape. A vibrating gyrosensor preferably has asmaller size and higher performance with reduction in size and weightand increases in functionality and performance of a main body device onwhich the vibrating gyrosensor is mounted. However, it has beendifficult to manufacture a small vibrating element with high precisiondue to the limit of machining precision.

Therefore, there has recently been proposed a vibrating gyrosensorincluding a cantilever vibrating element formed by laminating a pair ofelectrode layers with a piezoelectric thin film layer providedtherebetween on a silicon substrate using a thin film technique forsemiconductor processes (refer to, for example, Japanese UnexaminedPatent Application Publication No. 7-113643). Such a vibratinggyrosensor may be reduced in size and thickness and thus complexed orincreased in functionality by combination with a sensor for otherpurposes.

SUMMARY OF THE INVENTION

A mechanism for correcting motion blurring of a video camera or the likeis preferably adapted to detect rotation angles around at least theX-axis and Y-axis directions and thus generally includes two gyrosensorsfor detecting the rotation angles around the X-axis and Y-axisdirections. Therefore, even if a gyrosensor is reduced in size,reduction in the whole size of a usual mechanism for correcting motionblurring is limited.

A vibrating gyrosensor may be packaged by a method in which a vibratingelement having vibrators in two axes is formed on a silicon wafer usingthe above-described semiconductor technique (refer to JapaneseUnexamined Patent Application Publication No. 7-190783). However, alarge space is used for forming a two-axis integrated vibrating elementon a silicon wafer, thereby causing the problem of a low material yield.In addition, a two-axis integrated vibrating element has the problem ofcrosstalk between vibrators in the two axes accompanying with reductionin size.

The structure of a usual vibrating gyrosensor is complicated by ameasure against the above-described problems, and the realization ofreduction in size and thickness becomes more difficult. Namely, when twovibrators are provided for two-axis vibrations in a mechanism forcorrecting motion blurring, the realization of reduction in size becomesmore difficult, and the realization of a desired small package includingthe above-described two-axis integrated vibrating element also becomesdifficult.

It is desirable to provide a vibrating gyrosensor capable of detectingvibrations in two axes while decreasing the size, improving thecharacteristics, or decreasing the cost.

In accordance with an embodiment of the invention, there is provided avibrating gyrosensor including a support substrate on which a wiringpattern having a plurality of lands is formed, and vibrating elementsmounted on a surface of the support substrate, wherein at least twovibrating elements are mounted on the support substrate, for detectingvibrations in different axis directions.

In the above-described vibrating gyrosensor, the two vibrating elementsincluding respective vibrator parts having different axial directionsare mounted on the support substrate, and thus the vibrating elementsindependently detect detection signals in two axis directions.Therefore, each of the vibrating elements is efficiently produced at lowcost, and the operation of each vibrating element is stabilized toimprove reliability.

In the vibrating gyrosensor, each of the vibrating elements includes abase part having a mounting surface on which a plurality of terminalparts to be connected to lands on the support substrate is formed, and avibrator part integrally projected in a cantilever manner from one ofthe sides of the base part and having a substrate-facing surfacecoplanar with the mounting surface. The vibrator part has a firstelectrode layer, a piezoelectric layer, and a second electrode layer,which are formed on the substrate-facing surface in that order. The twovibrating elements are mounted so that the vibrator parts are disposedon axial lines at 90°.

In the vibrating gyrosensor, an AC electric field at a predeterminedfrequency is applied to each of the vibrating elements from a drivingdetector circuit part to produce a natural vibration in the vibratorpart. Also, when displacement occurs in each vibrator part by theCoriolis force produced by motion blurring, the displacement is detectedby the piezoelectric layer to output detection signals with oppositepolarities from a pair of detection electrodes. The detection signalsare processed by the driving detector circuit part to output as anangular velocity signal.

In this case, the difference between the operating frequencies of thevibrating elements is 1 kHz or more, thereby decreasing a crosstalkbetween the axes.

In the vibrating gyrosensor, at least two vibrating elements fordetecting vibrations in different axial directions are mounted on asupport substrate, thereby simplifying the structure, reducing the size,and permitting high-precision detection operations in two axisdirections. Also, each vibrating element is improved in productivity andmanufactured with high precision, thereby decreasing the cost andincreasing precision.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the whole of a vibrating gyrosensoraccording to a first embodiment of the present invention, with a covermember removed;

FIG. 2 is a sectional view of a principal portion of a vibrating elementof the vibrating gyrosensor shown in FIG.

FIG. 3 is a sectional view of a principal portion of the vibratingelement of the vibrating gyrosensor shown in FIG. 2 in a state in whichthe vibrating gyrosensor is mounted on a control substrate;

FIG. 4 is a bottom view of the vibrating element;

FIG. 5 is a bottom view of the vibrating gyrosensor;

FIG. 6 is a plan view of a support substrate showing a modified exampleof the structure of a load buffering part;

FIG. 7 is a block diagram of a circuit of the vibrating gyrosensor;

FIG. 8 is a perspective view of the whole of the vibrating element, asviewed from the bottom;

FIG. 9 is a perspective view of a vibrator part of the vibratingelement;

FIG. 10 is a flow chart of main steps of a method for manufacturing thevibrating gyrosensor;

FIG. 11 is a plan view of a silicon substrate used in a process formanufacturing a vibrating element;

FIG. 12 is a sectional view of the silicon substrate shown in FIG. 11;

FIG. 13 is a plan view of the silicon substrate on which vibratingelement formation portions are formed in a photoresist layer bypatterning;

FIG. 14 is a sectional view of the silicon substrate shown in FIG. 13;

FIG. 15 is a plan view of the silicon substrate on which vibratingelement formation portions are formed in a silicon oxide film bypatterning;

FIG. 16 is a sectional view of the silicon substrate shown in FIG. 15;

FIG. 17 is a plan view of the silicon substrate in which etched recessesare formed, the etched recesses constituting respective diaphragm partswhich define the thicknesses of the respective vibrator parts;

FIG. 18 is a sectional view of the silicon substrate shown in FIG. 17;

FIG. 19 is an enlarged sectional view of one etched recess;

FIG. 20 is a sectional view of a principal portion in which a firstelectrode layer, a piezoelectric film layer, and a second electrodelayer are laminated on each diaphragm part;

FIG. 21 is a plan view of a principal portion in which a drivingelectrode layer and detection electrodes are patterned in the secondelectrode layer shown in FIG. 20;

FIG. 22 is a sectional view of the principal portion shown in FIG. 21;

FIG. 23 is a plan view of a principal portion in which a piezoelectricthin film layer is patterned in the piezoelectric film layer shown inFIG. 20;

FIG. 24 is a sectional view of the principal portion shown in FIG. 23;

FIG. 25 is a plan view of a principal portion in which a referenceelectrode layer is patterned in the first electrode layer shown in FIG.20;

FIG. 26 is a sectional view of the principal portion shown in FIG. 25;

FIG. 27 is a plan view of a principal portion in which a planarizinglayer is formed;

FIG. 28 is a sectional view of the principal portion shown in FIG. 27;

FIG. 29 is a plan view of a principal portion in which leads are formedin respective formation regions on a base part;

FIG. 30 is a sectional view of the principal portion shown in FIG. 29;

FIG. 31 is a plan view of a principal portion in which a photoresistlayer is formed for forming an insulating protective layer;

FIG. 32 is a sectional view of the principal portion shown in FIG. 31 inwhich a first alumina layer of the insulating protective layer isformed;

FIG. 33 is a sectional view of the principal portion shown in FIG. 31 inwhich a silicon oxide layer of the insulating protective layer isformed;

FIG. 34 is a sectional view of the principal portion shown in FIG. 31 inwhich a second alumina layer of the insulating protective layer and anetching stop layer are formed;

FIG. 35 is a plan view of a principal portion in which an outside grooveis formed for forming the outside shape of a vibrator part;

FIG. 36 is a sectional view of the principal portion shown in FIG. 35,as viewed from a direction perpendicular to the longitudinal directionof the vibrator part;

FIG. 37 is a sectional view of the principal portion shown in FIG. 35,as viewed from the longitudinal direction of the vibrator part;

FIGS. 38A and 38B are sectional side views illustrating a method forforming plating bumps of a vibrating element;

FIGS. 39A, 39B, and 39C are drawings illustrating a step for adjusting avibrator part;

FIG. 40 is a table showing comparison of the numbers of the elementsobtained from a silicon substrate;

FIG. 41 is a graph showing the interference between axes due to anarrangement of vibrating elements;

FIGS. 42A and 42B are histograms of an angular shift of a vibratingelement in a mounting step, in which FIG. 42A shows mounting byrecognition of alignment marks, and FIG. 42B shows mounting byrecognition of an outer shape;

FIG. 43 is a graph showing the results of measurement of the magnitudeof an interference signal produced due to a frequency difference betweenthe different operating frequencies of two vibrating elements;

FIG. 44 is a graph showing the relation among the laser processingposition, the resonance frequency, and the degree of detuning;

FIG. 45 is a plan view schematically showing a laser processing positionfor adjusting the degree or detuning and a laser processing position foradjusting the resonance frequency of a vibrator part;

FIG. 46 is a plan view of a principal portion of a usual vibratinggyrosensor described in a second embodiment of the invention;

FIG. 47 is a plan view of a principal portion of a vibrating gyrosensoraccording to the second embodiment;

FIG. 48 is a graph showing the results of measurement of examplesaccording to the second embodiment;

FIG. 49 is a schematic view showing the relation between a vibratingelement and a driving detector circuit part according to a thirdembodiment of the invention;

FIG. 50 is a graph illustrating an operation of the vibrating elementshown in FIG. 49;

FIG. 51 is a graph showing an example of the relation between thepiezoelectric property and offset voltage of a piezoelectric material;and

FIG. 52 is a diagram showing a hysteresis loop of a piezoelectricmaterial.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Vibrating gyrosensors according to embodiments of the present inventionwill be described in detail below with reference to the drawings.

The present invention is not limited to these embodiments, and variousmodifications may be made on the basis of the technical idea of theinvention. Although each of parts of component members will be describedbelow using specified dimension values, each dimension value is acentral reference value. Also, the dimension values of each part are notlimited to these central reference values, and each part may be formedwith dimension values within a general tolerance range. Furthermore, thedimension values of the vibrating gyrosensors are not limited to thesedimension values, and each part may be appropriately formed according tocharacteristic specifications.

First Embodiment

(Schematic Configuration of Vibrating Gyrosensor)

Referring to FIG. 1, a vibrating gyrosensor 1 has an exterior memberincluding a support substrate 2 and a cover member 15 combined with afirst main surface 2-1 of the support substrate 2 to form a componentmounting space 3. For example, the vibrating gyrosensor 1 is mounted ona video camera to serve as a mechanism for correcting motion blurring.Also, for example, the vibrating gyrosensor 1 is used for a virtualreality device to serve as a motion detector or used for a carnavigation system to serve as a direction detector.

The vibrating gyrosensor 1 includes, for example, a ceramic substrate ora glass substrate as the support substrate 2. Also, a predeterminedwiring pattern 5 having a plurality of lands 4 is formed on the firstmain surface 2-1 of the support substrate 2 to form a component mountingregion 6. In the component mounting region 6 are mixed-loaded a pair offirst and second vibrating elements 20X and 20Y (hereinafter genericallyreferred to as “vibrating elements 20” unless otherwise specified),which are mounted to detect vibrations in different axial directions andwhich will be described in detail below, an IC circuit element 7, andmany external ceramic capacitors and electronic components 8.

In the component mounting region 6 of the support substrate 2, thevibrating elements 20 as well as the IC circuit element 7 and theelectronic components 8 are surface-mounted by a flip-chip process usinga proper mounting machine. The pair of the vibrating elements 20X and20Y having the same shape is mounted at the opposite corners 2C-1 and2C-2 of the first main surface 2-1 of the support substrate 2 so as tohave different axial lines. As shown in FIG. 2, each of the vibratingelements 20 has a base part 22 having a mount surface on which aplurality of terminals 25 to be connected to the respective lands 4through gold bumps 26 is formed, and a vibrator part 23 integrallyprojected from one of the sides of the base part 22 in a cantilevermanner. The structure of each vibrating element 20 will be described indetail below.

As shown in FIG. 1, the base part 22 of the first vibrating element 20Xis fixed to a floating island-like first vibrating element mountingregion 13A formed at the corner 2C-1 of the component mounting region 6of the support substrate 2, and the vibrator part 23 integrallyprojected from the base part 22 is directed toward the corner 2C-3adjacent to the corner 2C-1 along the side edge of the support substrate2. The base part 22 of the other second vibrating element 20Y is fixedto a floating island-like second vibrating element mounting region 13Bformed at the corner 2C-2 of the component mounting region 6 of thesupport substrate 2, and the vibrator part 23 integrally projected fromthe base part 22 is directed toward the corner 2C-3 adjacent to thecorner 2C-2 along the side edge of the support substrate 2.

In other words, the first and second vibrating elements 20X and 20Y aremounted at an angle of 90° on the support substrate 2 so that thevibrator parts 23 are directed toward the corner 2C-3. The vibratinggyrosensor 1 is adapted to detect vibrations in two axial directionsperpendicular to each other using the pair of the vibrating elements 20Xand 20Y. However, the vibrating elements 20X and 20Y may be mounted atan appropriate angle on the support substrate 2 according to thespecifications of a main body device.

The vibrating gyrosensor 1 detects angular velocities around thelongitudinal directions of the vibrator parts 23 of the vibratingelements 20 in a state in which the vibrators 23 are resonated. In thevibrating gyrosensor 1, the first and second vibrating elements 20X and20Y are mounted at an angle on the support substrate 2, forsimultaneously detecting the angular velocities around the X-axis andY-axis directions. For example, in a video camera, the vibratinggyrosensor 1 serves as a motion blur correcting mechanism which outputsa control signal based on a vibration state due to motion blurring.

Next, the configuration of the support substrate 2 will be described indetail.

(Load Buffering Structure)

The vibrating gyrosensor 1 may be decreased in size and thickness bythinning the support substrate 2. Therefore, strain or stress may occurin the support substrate 2 due to an external load such as vibration, animpact, or the like which is applied from the outside. In thisembodiment, a buffer structure for an external load is provided on thesupport substrate 2, for decreasing the influence on the vibratingelements 20 mounted on the support substrate 2 even when strain orstress occurs.

As shown in FIGS. 1 to 3, first load buffering grooves 12A and 12B(hereinafter generically referred to as “first load buffering grooves12” unless otherwise specified) are formed at the corners 2C-1 and 2C-2,respectively, of the first main surface 2-1. The vibrating elementmounting regions 13A and 13B (hereinafter generically referred to as the“vibrating element mounting regions 13” unless otherwise specified) areformed in regions surrounded by the respective first load bufferinggrooves 12, and the vibrating elements 20 are mounted on the respectivevibrating element mounting regions 13.

As shown in FIG. 3, in the support substrate 2, second load bufferinggrooves 14 are formed in a second main surface 2-2 to be mounted on anexternal control substrate 100 of the main body device or the like. Asshown in FIG. 5, the second load buffering grooves 14 include secondload buffering grooves 14A and 14B (generically referred to as “secondload buffering grooves 14” hereinafter unless otherwise specified). Asshown in FIG. 5, regions surrounded by the second load buffering grooves14 serve as terminal formation regions 115A and 115B (hereinaftergenerically referred to as the “terminal formation regions 115” unlessotherwise specified).

As shown in FIG. 4, each of the first load buffering grooves 12 isformed in a frame-like groove having a bottom, for forming the vibratingelement mounting region 13 larger than the outer shape of the base part22 of each vibrating element 20. The first load buffering grooves 12 areformed by, for example, mechanical grooving with a dicer, chemicalgrooving by wet etching, or dry etching with a laser. Each of the firstload buffering grooves 12 is formed to a depth of 100 μm or more withina range in which the mechanical strength of the support substrate 2 isnot impaired.

As shown in FIG. 5, the second load buffering grooves 14A and 14B areformed in parallel along the peripheral side lines of the supportsubstrate 2. The regions between the peripheral side lines and therespective second load buffering grooves 14A and 14B serve as theterminal formation regions 115A and 115B, respectively, in each of whicha plurality of mounting terminal parts 116A or 116B (hereinaftergenerically referred to as the “mounting terminal parts 116” unlessotherwise specified) is appropriately arranged. The support substrate 2is mounted on the control substrate 100 by connecting the mountingterminal parts (external connection terminals) 116 to the respectivelands on the control substrate 100 through bumps 117 provided on therespective mounting terminal parts 116.

Like the first load buffering grooves 12, each of the second loadbuffering grooves 14 is formed to a predetermined depth in the secondmain surface 2-2 of the support substrate 2 by mechanical grooving witha dicer, chemical grooving by wet etching, or dry etching with a laseror the like. The second load buffering grooves 14 form the floatingisland-like terminal formation regions 115 on the second main surface2-2 of the support substrate 2, and a plurality of the mounting terminalparts 116 is arranged in each of the terminal formation regions 115along the outer edge of the support substrate 2. The second loadbuffering grooves 14 are not limited to linear grooves along the outeredge, and the second load buffering grooves 14 may be formed in, forexample, a frame shape surrounding each mounting terminal part 116 or asubstantially U-shaped form with both ends open to the outer edge.

In the support substrate 2, many via holes are formed to pass throughthe first and second main surfaces 2-1 and 2-2 so that the wiringpattern 5 on the first main surface 2-1 is appropriately connected tothe mounting terminal parts 116 on the second main surface 2-2 throughthe via holes.

When an impact is applied to the main body device, strain or stressoccurs in the support substrate 2 of the vibrating gyrosensor 1 throughthe control substrate 100. In this embodiment, as described above, eachof the vibrating elements 20 is mounted on the floating island-likevibrating element mounting region 13 surrounded by the first loadbuffering groove 12. Consequently, the strain or stress occurring by anexternal load is absorbed by the first load buffering groove 12.Therefore, each of the first load buffering grooves 12 functions as adamper for decreasing the influence of an external load on the vibratingelement 20 mounted on the vibrating element mounting region 13, therebypermitting a stable detection operation of the vibrating element 20.

On the other hand, in the vibrating gyrosensor 1, as described above,the second load buffering grooves 14 are provided so that the mountingterminal parts 116 provided on each of the floating island-like terminalformation regions 115 serve as portions fixed to the control substrate100. In this embodiment, an external load transmitted through thecontrol substrate 100 is absorbed by the second load buffering grooves14. Therefore, each of the second load buffering grooves 14 functions asa damper for decreasing the influence of an external load on thevibrating element 20 mounted on the vibrating element mounting region13, thereby permitting a stable detection operation of the vibratingelement 20.

Each of the first load buffering grooves 12 is formed into a continuousgroove having a U-shaped sectional form, but each load burring groove 12is not limited to this. Each of the first load buffering grooves 12 maybe formed by, for example, arranging many grooves to form a frame shapeas a whole on condition that a predetermined characteristic issatisfied. Also, each of the second load buffering grooves 14 is notlimited to a continuous groove, and each of the second load bufferinggrooves 14 may be formed by, for example, arranging many grooves.Furthermore, although the first load buffering grooves 12 and the secondload buffering grooves 14 are formed in the first main surface 2-1 andthe second main surface 2-2, respectively, of the support substrate 2,to form a load buffering structure including the front and backsurfaces, only the first load buffering grooves 12 or the second loadbuffering grooves 14 may be provided to form a load buffering structureon condition that a predetermined characteristic is satisfied.

Although, as descried above, each of the frame-like first load burringgrooves 12 is formed in the first main surface 2-1 of the supportsubstrate 2 to surround the vibrating element mounting region 13, thestructure of each first load burring groove is not limited to this. In avibrating gyrosensor 170 shown in FIG. 6, frame-like first loadbuffering grooves 172X and 172Y are formed in a support substrate 171,and cross-shaped partition grooves 173A and 173B are further formed ineach first load buffering groove 172 to form four mounting regions 174Ato 174D.

Namely, in the vibrating gyrosensor 170, the individual mounting regions174 are partitioned corresponding to the respective terminal parts 25formed on the base part 22 of each vibrating element 20. Although notshown in FIG. 6, a mounting terminal part is provided in each mountingregion 174. In the vibrating gyrosensor 170 having the above-describedstructure, each of vibrating elements 20 is mounted on the supportsubstrate 171 by fixing the terminal parts 25 to the correspondingmounting terminal parts through gold bumps so that the terminal parts 25are fixed to respective second floating islands which are divided by thepartition grooves 173 in a first floating island entirely surrounded byeach first load buffering groove 172.

(Space Forming Recess)

In the support substrate 2, recesses 11A and 11B (hereinaftergenerically referred to as “space forming recesses 11” unless otherwisespecified) are formed in the component mounting region 6 correspondingto the vibrating elements 20X and 20Y, for forming spaces in which therespective vibrator parts 23 are freely vibrated in the thicknessdirection. Each of the space forming recesses 11 is formed into arectangular groove with a bottom which has a predetermined depth and anaperture dimension by, for example, etching or grooving the first mainsurface 2-1 of the support substrate 2.

In the vibrating gyrosensor 1, the vibrating elements 20 each includingthe base part 22 and the cantilever vibrator part 23, which areintegrally formed, are mounted on the first main surface 2-1 of thesupport substrate 2 through the gold bumps 26. The space between thevibrator part 23 of each of the vibrating elements 20 and the first mainsurface 2-1 of the support substrate 2 is determined by the thickness ofthe gold bumps 26, for decreasing the thickness of the whole structure.However, a sufficient space may not be maintained due to the processinglimitation of the gold bumps 26.

Each vibrating element 20 produces an air flow between the first mainsurface 2-1 of the support substrate 2 and the vibrating element 20 witha vibration operation of the vibrator part 23. The air flow collideswith the first main surface 2-1 of the support substrate 2 to cause thedamping effect of pushing upward each vibrator part 23. In thisembodiment, the space forming recesses 11 are formed in the first mainsurface 2-1 of the support substrate 2, and thus a sufficient space m ismaintained between the first main surface 2-1 and each vibrator part 23,as shown in FIG. 2, thereby decreasing the damping effect on thevibrating elements 20.

In the vibrating gyrosensor 1, the vibrating elements 20 are mounted onthe first main surface 2-1 of the support substrate 2 so that thevibrator parts 23 extend opposite to the respective space formingrecesses 11, and thus a sufficient space is maintained between each ofthe vibrator parts 23 and the support substrate 2 while maintaining thesmall thickness of the vibrating gyrosensor 1, as shown in FIG. 2. As aresult, when the vibrator parts 23 vibrate in the thickness direction,the damping effect is decreased, thereby securing a stable detectionoperation of each vibrating element 20.

The space forming recesses 11 are optimized according to the dimensionsof the vibrator parts 23 of the vibrating elements 20 and formed in thesupport substrate 2. In this embodiment, when each of the vibratingelements 20 is formed with dimension values, which will be describedbelow, the aperture dimension of each of the space forming recesses 11is 2.1 mm×0.32 mm and the depth dimension k (refer to FIG. 2) isk≧p/2+0.05 mm wherein p is the maximum amplitude of the vibrator parts23. When the space forming recesses 11 having this structure are formedin the support substrate 2, the height dimension is suppressed to permitthinning, and the influence of the damping effect on the vibratingelements 20 is decreased to maintain a high Q factor and permit stabledetection of a motion such as motion blurring or the like with highsensitivity.

Next, the structure of the vibrating elements 20 will be described indetail.

(Gold Bump)

Each of the vibrating elements 20 is mounted on the vibrating elementmount region 13 so that the second main surface (22-2) of the base part22, which includes a second main surface 21-2 of a silicon substrate 21as described below, forms a fixed surface (mounting surface) to thesupport substrate 2. As shown in FIG. 4, first to fourth terminal parts25A to 25D (hereinafter generically referred to as “terminal parts 25”unless otherwise specified) are formed on the mounting surface 22-2 ofthe base part 22, and first to fourth gold bumps 26A to 26D (hereinaftergenerically referred to as “gold bumps 26” unless otherwise specified)are formed as metal protrusions on the terminal parts 25, respectively.

The terminal parts 25 of each vibrating element 20 are formedcorresponding to the respective lands 4 formed in the wiring pattern 5on the support substrate 2. Therefore, each of the terminal parts 25 isaligned with the corresponding land 4 and combined with the supportsubstrate 2. In this state, the vibrating elements 20 are pressedagainst the support substrate 2 under application of ultrasonic waves toweld the terminal parts 25 to the respective lands 4 through the goldbumps 26. As a result, the vibrating elements 20 are mounted on thesupport substrate 2. In this way, when the vibrating elements 20 aremounted with the gold bumps 26 having a predetermined height, each ofthe vibrator parts 23 performs a predetermined vibration motion whilethe second main surface (substrate-facing surface) 23-2 being maintainedat a predetermined height from the first main surface 2-1 of the supportsubstrate 2.

In this embodiment, the efficiency of the mounting step is improved bysurface-mounting the vibrating elements 20 on the support substrate 2.The connectors used in the surface-mounting process are not limited tothe above-descried gold bumps 26, and various other metal protrusionsgenerally used in semiconductor processes, such as solder balls, copperbumps, or the like, may be used. In this embodiment, a process formanufacturing the main body device includes reflow soldering forconnecting and fixing the mounting terminal parts 116 of the supportsubstrate 2 to respective lands of the control substrate 100 throughbumps 117, and thus the gold bumps 26 having high heat resistance andhigh workability are used as the connectors.

In a vibrating gyrosensor, mechanical quality factor (Q factor) isdetermined by a structure for fixing a vibrating element to a supportsubstrate. In this embodiment, the vibrating elements 20 are mounted onthe support substrate 2 through the gold bumps 26 so that the base part22 floats on the first main surface 2-1 of the support substrate 2.Therefore, the damping rate at the end of each vibrator part 23 isincreased to achieve a satisfactory Q factor, as compared with a case inwhich a base part is entirely bonded to a support substrate, forexample, through an adhesive layer. In addition, when the base part 22is fixed at a plurality of positions of the first main surface 2-1 ofthe support substrate 2, a satisfactory Q factor is obtained as comparedwith a structure in which the base part 22 is fixed at one position.Therefore, the base part 22 is fixed at the four corners on the supportsubstrate 2, thereby achieving a satisfactory Q factor.

The gold bumps 26 may be provided in such a manner that the center ofgravity of the whole is positioned in the range of the width dimensiont6 (refer to FIG. 9) with respect to the longitudinal center axis ofeach vibrator part 23. By disposing the gold bumps 26 in this manner,each vibrator part 23 may stably vibrate in the thickness directionwithout breaking a transverse balance.

Furthermore, each of the gold bumps 26 is formed outside a region havinga radius of 2 times the width dimension t6 of the vibrator parts 23 fromthe base end of each vibrator part 23 projected from the base part 22.Therefore, the operation of absorbing the vibration of the vibrator part23 by the gold bumps 26 is decreased to maintain the high Q factor.

In addition, at least one gold bump 26 is formed within a region of 2times the thickness dimension t1 (refer to FIG. 8) of the base part 22from the base end of each vibrator part 23. Therefore, the vibration ofeach vibrator part 23 is not transmitted to the base part 22, therebypreventing the occurrence of a shift of the resonance frequency.

Furthermore, each of the gold bumps 26 may be a two-stage bump, andfifth gold bumps may be formed as dummies not involved in electricconnection on the second main surface of each of the base parts 22. Inthis case, of course, dummy terminal parts to which the respective fifthgold bumps are welded are formed on the support substrate 2.

(Element Shape)

As shown in FIG. 8, in each of the vibrating elements 20 according tothis embodiment, the vibrator part 23 has the second main surface(substrate-facing surface) 23-2 coplanar with the second main surface(mounting surface) 22-2 of the base part 22 and is projected in acantilever manner in which one end is integrated with the base part 22.As shown in FIG. 2, the vibrator part 23 has an upper surface 23-1stepped down from the first main surface (upper surface) 22-1 of thebase part 22 so as to have a predetermined thickness. The vibrator part23 has predetermined length and sectional area and includes a cantileverbeam formed integrally with one side 22-3 of the base part 22 and havinga rectangular cross-section.

Also, as shown in FIG. 8, the base part 22 of each vibrating element 20has a thickness t1 of 300 μm, a length dimension t2 of 3 mm to the tipof the vibrator part 23, and a width dimension t3 of 1 mm. As shown inFIG. 9, the vibrator part 23 of each vibrating element 20 has athickness dimension t4 of 100 μm, a length dimension t5 of 2.5 mm, and awidth dimension t6 of 100 μm. As described in detail below, each of thevibrating elements 20 vibrates with a driving voltage at a predeterminedfrequency applied from a driving detector circuit part 50, but vibratesat a resonance frequency of 40 kHz due to the above-descried shape. Thestructure of each vibrating element 20 is not limited to theabove-described structure, and the structure may be variously determinedaccording to the frequency used and the intended whole shape.

Furthermore, each of the vibrating elements 20 may be formed so as tosatisfy the conditions below for each of the base part 22 and thevibrator part 23. Namely, each base part 22 is formed with a widthdimension t3 which is 2 times or more the width dimension t6 of thevibrator part 23, and the center of gravity is positioned within aregion of 2 times the width dimension t6 of the vibrator part 23 withrespect to the longitudinal center axis of the vibrator part 23. In thisstructure, each vibrator part 23 satisfactorily vibrates withoutbreaking a transverse balance. In addition, when the thickness dimensiont1 of each base part 22 is 1.5 times the thickness dimension of thevibrator part 23, the mechanical strength of the base part 22 ismaintained to prevent the base part 22 from vibrating due to thevibration of the vibrator part 23, thereby preventing the occurrence ofa shift of the resonance frequency.

(Piezoelectric Film and Various Electrode Layers)

In each of the vibrating elements 20, as shown in FIG. 4, a referenceelectrode layer (first electrode layer) 27, a piezoelectric thin filmlayer 28, and a driving electrode layer (second electrode layer 28) arelaminated on the second main surface (substrate-facing substrate) 23-2of the vibrator part 23 over the entire length in the length directionin the process for producing the vibrating elements, which will bedescribed below. Also, a pair of detection electrodes 30R and 30L(hereinafter generically referred to as “detection electrodes 30” unlessotherwise specified) is formed with the driving electrode layer 29therebetween on the second main surface (substrate-facing surface) 23-2of each vibrator part 23. The driving electrode layer 29 and thedetection electrodes 30 constitute the second electrode layer.

The reference electrode layer 27 serving as the first layer is formed onthe second main surface (substrate-facing surface) 23-2 of each vibratorpart 23, and the piezoelectric thin film layer 28 having substantiallythe same length as that of the reference electrode layer 27 is formedthereon. The driving electrode layer 29 having substantially the samelength as that of the piezoelectric thin film layer 28 and a smallerwidth than that thereof is formed at the central portion of thepiezoelectric thin film layer 28 in the width direction. Furthermore,the pair of the detection electrodes 30R and 30L is laminated on thepiezoelectric thin film layer 28 to hold the driving electrode layer 29therebetween.

(Lead and Terminal Part)

As shown in FIG. 4, in each of the vibrating elements 20, a first lead31A is formed on the second main surface (mounting surface) 22-2 of thebase part 22, for connecting the reference electrode layer 27 to thefirst terminal part 25A, and a third lead 31C is formed for connectingthe driving electrode layer 29 to the third terminal part 25C.Similarly, on the mounting surface 22-2 of the base part 22, a secondlead 31B is formed for connecting the first detection electrode 30R tothe second terminal part 25B, and a fourth lead 31D is formed forconnecting the second detection electrode 30L to the fourth terminalpart 25D. Hereinafter, the leads 31A to 31D are generically referred toas “leads 31” unless otherwise specified.

The first lead 31A is integrally extended from the base end of thereference electrode layer 27 formed on each vibrator part 23 to the basepart 22 and connected to the first terminal part 25A formed at a cornerof the second main surface (mounting surface) 22-2 of the base part 22on the side to which the vibrator part 23 is integrally formed. Thedriving electrode layer 29 and the detection electrodes 30 each have aslightly wide base end extending from the vibrator part 23 to the basepart 22, the slightly wide base ends being covered with a planarizinglayer 24.

The second lead 31B is formed so that an end thereof crosses over theplanarizing layer 24, extended to the rear corner opposite to the firstterminal part 25A along one side of the base part 22, and connected tothe second terminal part 25B formed at this corner. The third lead 31Cis formed so that an end crosses over the planarizing layer 24, extendedrearward through a substantially central portion of the base part 22 andalso extended to a corner opposite to the second terminal part 25B alongthe rear side end, and connected to the third terminal part 25C formedat this corner. The fourth lead 31D is also formed so that an endcrosses over the planarizing layer 24, extended to the other corneropposite to the third terminal part 25C on the front side along theother side of the base part 22, and connected to the fourth terminalpart 25D formed at this corner.

In each of the vibrating elements, the terminal parts 25 are formed atproper optimum positions with a proper number on the second main surface(mounting surface) 22-2 of the base part 22 regardless of theabove-descried structure. Also, in each of the vibrating elements 20, ofcourse, the connection pattern between the leads of the electrode layersand the respective terminal parts 25 is not limited to the above, andthe connection pattern is appropriately formed on the second surface ofeach base part 22 according to the positions and number of the terminalparts 25.

(Insulating Protective Layer)

In each of the vibrating elements 20, as shown in FIGS. 2 and 4, aninsulating protective layer 45 is formed on the second main surface 21-2to cover the base part 22 and the vibrator part 23. The insulatingprotective layer 45 has a three-layer structure including a firstalumina (aluminum oxide: Al₂O₃) layer 46 as a first layer, a siliconoxide (SiO₂) layer 47 as a second layer, and a second alumina layer 48as a third layer.

As shown in FIG. 2, the insulating protective layer 45 has a terminalaperture 49 corresponding to the formation region of each of theterminal parts 25 so that each terminal part 25 is exposed to theoutside through the terminal aperture 49. In each of the vibratingelements 20, as shown in FIG. 2, the gold bump 26 is formed on eachterminal part 25 so as to project from the terminal aperture 49.

The insulating protective layer 45 is formed so that the second mainsurface 21-2 of the silicon substrate 21 is exposed in a frame formbetween the outer peripheries of each base part 22 and each vibratorpart 23 and the outer peripheries of the reference electrode layer 27and the terminal parts 25. The insulating protective layer 45 is formedso as not to cover the exposed peripheral portion of the second mainsurface 21-2, thereby preventing peeling of the insulating protectivelayer 45 from the peripheral region during the step of cutting out eachvibrating element 20, which will be described below. The insulatingprotective layer 45 is formed with a width dimension of, for example, 98μm, in each vibrator part 23 having a width dimension t6 of 100 μm.

The insulating protective layer 45 includes the first alumina layer 46having a thickness dimension of, for example, 50 nm. The first aluminalayer 46 functions as an under adhesive layer for improving the adhesionto the main surfaces of the base part 22 and the vibrator part 23.Therefore, the insulating protective layer 45 is strongly deposited oneach vibrator part 23 performing vibration to prevent the occurrence ofpeeling or the like.

The silicon oxide layer 47 functions to cut off moisture and the like inair and prevent the adhesion thereof to each electrode layer, and alsofunctions to suppress oxidation of each electrode layer, electricallyinsulate each electrode, or mechanically protect each electrode thinfilm layer and the piezoelectric thin film layer 28. The uppermostsecond alumina layer 48 functions to improve the adhesion to a resistlayer formed for forming each vibrator part 23 on the silicon substrate21 by a outer shape grooving step, which will be described below, andprevent damage to the silicon oxide layer 47 with an etching agent.

The silicon oxide layer 47 is formed to a thickness of at least twotimes the thickness of a second electrode layer 42 and 1 μm or less.Also, the silicon oxide layer 47 is deposited on the first alumina layer46 by sputtering in an argon gas atmosphere at 0.4 Pa or less. Since thesilicon oxide layer 47 has the above-described thickness, the insulatingprotective layer 45 exhibits a sufficient insulating protective functionand prevents the occurrence of burr during deposition. The silicon oxidelayer 47 is formed with a high film density by deposition under theabove-described sputtering conditions.

(Alignment Mark)

In the vibrating gyrosensor 1, in order to precisely position and mountthe first and second vibrating elements 20X and 20Y having the sameshape on the support substrate 2, the position of each land 4 on thesupport substrate 2 is recognized with a mounting machine. Therefore,alignment marks 32A and 32B (hereinafter generically referred to as“alignment marks 32”) are provided on the first main surface (uppersurface) 22-1 of the base part 22 of each vibrating element 20, in orderto position and mount each vibrating element 20 on the correspondingland 4 recognized by the mounting machine.

As shown in FIGS. 1 and 4, the alignment marks 32 include a pair ofrectangular portions of a metal foil or the like formed with a spacetherebetween in the width direction on the first main surface (uppersurface) 22-1 of each base part 22. After the alignment marks 32 areread by the mounting machine to produce mounting data about the positionand attitude relative to the support substrate 2, each vibrating element20 may be precisely positioned and mounted on the support substrate 2 onthe basis of the mounting data and the data of the lands 4.

Although the alignment marks 32 are formed on the first main surface ofthe base part 22 of each vibrating element 20, the alignment marks arenot limited to this. The alignment marks 32 composed of, for example, aconductor, may be formed at proper positions avoiding the terminal parts25 and the leads 31 on the second main surface (mounting surface) 22-2of each base part 22, for example, at the same time as a wiring step. Asdescribed in detail below, the alignment marks 32 are preferablypositioned and formed in conformity with reference markers used forreactive etching using an inductively coupled plasma apparatus which isused for forming the electrode layers of each vibrating element 20 andused in the outer shape grooving step for forming the vibrator part 23.The alignment marks 32 may be formed with a precision of 0.1 μm or lesson each vibrator part 23 using a stepper exposure device.

The alignment marks 32 are formed by an appropriate method. For example,when the alignment marks 32 are formed on the second main surface(mounting surface) 22-2 of each base part 22 by patterning a firstelectrode layer 40 including a titanium layer and a platinum layer asdescribed below, the marks are read in the mounting step to obtain ahigh contrast in image processing, thereby improving the mountingprecision.

(Cover)

Next, the cover 15 for shielding the first main surface 2-1 of thesupport substrate 2 will be described in detail.

In the vibrating gyrosensor 1, displacement of each vibrating element 20due to the Coriolis force produced by motion blurring is detected by thepiezoelectric thin film layer 28 and the detection electrodes 30 formedon the vibrating element 20 to output a detection signal, as describedin detail below. When light is applied to the piezoelectric thin filmlayer 28, a voltage occurs due to a pyroelectric effect, and thepyroelectric voltage affects a detection operation to decrease thedetection properties.

In the vibrating gyrosensor 1, the component mounting space 3 formed bythe support substrate 2 and the cover member 15 is shielded from light,and thereby a decrease in the characteristics due to the influence ofexternal light is prevented. As shown in FIG. 1, the outer periphery ofthe support substrate 2 is stepped down from the first main surface 2-1along the whole periphery to flange the component mounting region 6 andform a light-shielding step 9 including a vertical wall, andconsequently a cover fixing part 10 is formed. The cover member 15including a metal thin plate is bonded, by resin bonding, to the coverfixing part 10 of the support substrate 2 over the whole periphery, andthus the component mounting region 6 is closed and made dustproof andmoisture proof and to form a light-shielding space.

As shown in FIG. 1, the cover member 15 is formed in a box-like shape asa whole, which includes a main surface part 16 having outer dimensionssufficient to cover the component mounting region 6 of the supportsubstrate 2 and a peripheral wall part 17 integrally formed by bendingthe main surface part 16 along the entire periphery thereof. The covermember 15 is formed with a height dimension sufficient to form thecomponent mounting space 3 in which the vibrator part 23 of eachvibrating element 20 vibrates when the peripheral wall part 17 iscombined with the support substrate 2. The cover member 15 has aperipheral flange 18 integrally formed by bending the peripheral wallpart 17 along the entire opening edge thereof, the peripheral flange 18being slightly narrower than the cover fixing part 10 formed in thesupport substrate 2. Although not shown in the drawings, the peripheralflange 18 has a ground projection to be connected to a ground terminalon the control substrate 100 when the vibrating gyrosensor 1 is mountedon the control substrate 100.

The cover member 15 includes a metal thin plate and thus maintains thelight weight of the vibrating gyrosensor 1. However, the cover member 15may not exhibit the sufficient light shielding function due to adecrease in the light shielding property for external light at theinfrared wavelengths. Therefore, according to this embodiment, allsurfaces of the main surface part 16 and the peripheral wall part 17 arecoated with, for example, an infrared absorbing paint, which absorbslight at the infrared wavelengths, to form a light shielding layer 19,so that radiation of external light at the infrared wavelengths into thecomponent mounting space 3 is cut off to permit a stable operation ofeach vibrating element 20. The light shielding layer 19 may be formed onboth the front and back main surfaces by dipping in an infraredabsorbing paint solution, or may be formed by black chromium plating,black dyeing, or black anodization.

As described above, in the vibrating gyrosensor 1, the cover member 15is combined with the support substrate 2 by placing the peripheralflange 18 on the cover fixing part 10 and bonding them together with anadhesive, thereby forming the closed, light-shielding component mountingspace 3. However, external light may pass through the adhesive disposedin the space between the cover fixing part 10 and the peripheral flange18 which are bonded together, and enter the component mounting space 3.In this embodiment, therefore, the cover fixing part 10 is stepped drawnfrom the main surface 1-2 of the support substrate 2 through the lightshielding step 9, as described above. As a result, external lighttransmitted through the adhesive layer is cut off by the light shieldingstep 9.

In this embodiment, like other component members, the cover member 15 iscombined with the support substrate 2 by the surface mounting method,and thus the assembly step is rationalized. In the vibrating gyrosensor1, since the cover member 15 is fixed to the stepped cover fixing part10 of the support substrate 2, the thickness is decreased, and adhesiveflowing into the component mounting region 6 is prevented. Also, thecomponent mounting space 3 functions as a dustproof and moisture-proofspace as well as a light-shielding space, thereby preventing theoccurrence of a pyroelectric effect in each vibrating element 20 andpermitting the stable detection of a motion such as motion blurring orthe like.

(Circuit Configuration)

Next, a circuit configuration for driving the vibrating gyrosensor 1will be described with reference to FIG. 7.

The vibrating gyrosensor 1 includes a first driving detector circuitpart 50X and a second driving detector circuit part 50Y which areconnected to the first vibrating element 20X and the second vibratingelement 20Y, respectively, and which each include the IC circuit element7, the electronic components 8, and the like. The first and seconddriving detector circuit parts 50X and 50Y have the same circuitconfiguration and are thus generically referred to as “driving detectorcircuit parts 50” hereinafter. Each of the driving detector circuitparts 50 include an impedance coveter circuit 51, an adding circuit 52,an oscillator circuit 53, a differential amplifier circuit 54, asynchronous detector circuit 55, and a DC amplifier circuit 56.

As shown in FIG. 7, in each of the driving detector circuit parts 50,the impedance converter circuit 51 and the differential amplifiercircuit 54 are connected to each of the first and second detectionelectrodes 30L and 30R of each vibrating element 20. The adding circuit52 is connected to the impedance converter circuit 51, and theoscillator circuit 53 connected to the adding circuit 52 is connected tothe driving electrode layer 29. The synchronous detector circuit 55 isconnected to the differential amplifier circuit 54 and the oscillatorcircuit 53, and the DC amplifier circuit 56 is connected to thesynchronous detector circuit 55. Furthermore, the reference electrodelayer 27 of each vibrating element 20 is connected to the referencepotential 57 on the support substrate 2.

In each of the driving detector circuit parts 50, the vibrating element20, the impedance converter circuit 51, the adding circuit 52, and theoscillator circuit 53 constitute a self-exited oscillator circuit. Whenoscillation voltage Vgo at a predetermined frequency is applied to thedriving electrode layer 29 from the oscillator circuit 53, naturaloscillation occurs in the vibrator part 23 of each vibrating element 20.The output Vgr from the first detection electrode 30R and the output Vglfrom the second detection electrode 30L of each vibrating element 20 aresupplied to the impedance converter circuit 51, and outputs Vzr and Vzlare output to the adding circuit 52 from the impedance converter circuit51 on the basis of the inputs Vgr and Vgl, respectively. The addingcircuit 52 outputs adding output Vsa to the oscillator circuit 53 on thebasis of these inputs.

The outputs Vgr and Vgl from the first and second detection electrodes30R and 30L, respectively, of each vibrating element 20 are supplied tothe differential amplifier circuit 54. When each vibrating element 20detects motion blurring, a difference occurs between the outputs Vgr andVgl in the driving detector circuit part 50, and thus a predeterminedoutput Vda is produced from the differential amplifier circuit 54. Theoutput Vda from the differential amplifier circuit 54 is supplied to thesynchronous detector circuit 55. The synchronous detector circuit 55synchronously detects the output Vda, converts it to a DC signal Vsd,and supplies the DC signal Vsd to the DC amplifier circuit 56 to outputthe DC signal Vsd after predetermined DC amplification.

The synchronous detector circuit 55 integrates the output Vda of thedifferential amplifier circuit 54 after full-wave rectification with thetiming based on a clock signal Vck which is output from the oscillatorcircuit 53 synchronously with the driving signal, thereby producing theDC signal Vsd. As described above, each of the driving detector circuitparts 50 amplifies the DC signal Vsd by the DC amplifier circuit 56 andthen outputs it, and, as a result, an angular velocity signal producedby motion blurring is detected.

In each of the driving detector circuit parts 50, the impedanceconverter circuit 51 produces low impedance output Z3 in ahigh-impedance input Z2 state to exhibit the function to separatebetween the impedance Z1 between the first and second detectionelectrodes 30R and 30L and the impedance Z4 between the inputs of theadding circuit 52. By providing the impedance converter circuit 51, alarge output difference is obtained from the first and second detectionelectrodes 30R and 30L.

In each of the driving detector circuit parts 50, the above-describedimpedance converter circuit 51 exhibits only the impedance convertingfunction for the input and output without significantly affecting themagnitude of a signal. Therefore, the magnitude of the output Vgr fromthe first detection electrode 30R is same as that of the output Vzr ofthe impedance converter circuit 51, and the magnitude of the output Vglfrom the second detection electrode 30L is the same as that of theoutput Vzl of the impedance converter circuit 51. In each of the drivingdetector circuit parts 50, even when the vibrating element 20 detectsmotion blurring to produce a difference between the output Vgr from thefirst detection electrode 30R and the output Vgl from the seconddetection electrode 30L, the difference is held in the output Vsa fromthe adding circuit 52.

In each of the driving detector circuit parts 50, for example, even whennoise is superposed by a switching operation or the like, componentsother than a resonance frequency component are removed by a functionsimilar to a band filter in the vibrating element 20 to remove the noisecomponent superposed on the output Vgo from the oscillator circuit 53,thereby obtaining the high-precision output Vda not including the noisecomponent from the differential amplifier circuit 54. In the vibratinggyrosensor 1, the driving detector circuit parts 50 are not limited tothe above. The driving detector circuit parts may be formed so thatdisplacement due to motion blurring of each vibrator part 23 performingnatural vibration is detected by the piezoelectric thin film layer 28and a pair of the detection electrodes 30, and detection output isobtained by appropriate processing.

As described above, the vibrating gyrosensor 1 includes the firstvibrating element 20X for detecting an angular velocity around theX-axis direction and the second vibrating element 20Y for detecting anangular velocity around the Y-axis direction. The first driving detectorcircuit part 50X connected to the first vibrating element 20X producesthe detection output VsdX in the X-axis direction, and the seconddriving detector circuit part 50Y connected to the second vibratingelement 20Y produces the detection output VsdY in the Y-axis direction.In the vibrating gyrosensor 1, the operating frequency of each of thefirst and second vibrating elements 20X and 20Y may be set in a range ofseveral kHz to several hundreds kHz. When a difference (fx−fy) betweenthe operating frequency fx of the first vibrating element 20X and theoperating frequency fy of the second vibrating element 20Y is 1 kHz ormore, cross talk is decreased to permit the precision detection ofvibration.

According to demand, the driving detector circuit parts 50 includerespective filter amplifier circuits for selectively amplifyingdetection signals at the operation frequencies fx and fy of thevibrating elements 20X and 20Y, which are contained in the outputs ofthe adding circuits 52, and supplying the amplified detection signals tothe oscillator circuits 53.

(Method for Manufacturing Vibrating Gyrosensor)

The method for manufacturing the vibrating gyrosensor 1 according tothis embodiment will be described below. FIG. 10 is a flow chart showingprincipal steps of the method for manufacturing the vibrating gyrosensor1.

The vibrating gyrosensor 1 is produced by simultaneously forming manyvibrating elements 20 using, as a base material, the silicon substrate21 which is cut out so that the main surface 21-1 is a (100) orientationplane, and the side 21-3 is a (110) orientation plane, as shown in FIGS.11 and 12, and then cutting the substrate into the respective vibratingelements 20 by a cutting step.

(Step of Preparing Substrate)

The outer dimensions of the silicon substrate 21 are determinedaccording to the specifications of the equipment used in the process,for example, 300×300 mm. The silicon substrate 21 is not limited to asubstrate having a rectangular planar shape as shown in FIG. 11, and awafer-shaped substrate having a circular planar shape may be used. Thethickness of the silicon substrate 21 is determined depending on theworkability, cost, and the like, but the thickness may be larger thanthe thickness dimension of at least the base part 22 of each vibratingelement 20. As described above, since the base part 22 has a thicknessof 300 μm, and the vibrator part 23 has a thickness of 100 μm, thesubstrate 21 having a thickness of 300 μm or more is used.

As shown in FIG. 12, silicon oxide films (SiO₂ films) 33A and 33B(generically referred to as “silicon oxide films 33” hereinafter unlessotherwise specified) are formed, by thermal oxidation, over the entiresurfaces of the first main surface 21-1 and the second main surface21-2, respectively, of the silicon substrate 21. The silicon oxide films33 function as protective films in anisotropic etching of the crystal ofthe silicon substrate 21, as described below. The silicon oxide films 33are formed to a proper thickness as long as a protective film functionis exhibited, but the silicon oxide films 33 are formed to a thicknessof, for example, about 0.3 μm.

(Step of Forming Etched Recess)

The process for producing the vibrating elements includes a step similarto a thin film step of a semiconductor process. Namely, the processincludes a step of etching the first main surface 21-1 of the siliconsubstrate 21 to form the etched recesses 37 with a predetermined depthdimension, for forming the vibrator parts 23 of the respective vibratingelements 20.

As shown in FIGS. 13 to 19, the etched recess forming step includes astep of forming a photoresist layer 34 on the first main surface 21-1 ofthe silicon substrate 21, a step of patterning the photoresist layer 34to form photoresist layer apertures 35 in the photoresist layer 34corresponding to the formation portions of the respective etchedrecesses 37, a first etching step of removing the silicon oxide film 33Aexposed in the photoresist layer apertures 35 to form silicon oxide filmapertures 36, and a second etching step of forming the etching recesses37 in the respective silicon oxide film apertures 36.

In the step of forming the photoresist layer, a photoresist material isapplied over the entire surface of the silicon oxide film 33A formed onthe first main surface 21-1 of the silicon substrate 21 to form thephotoresist layer 34. The step of forming the photoresist layer uses,for example, a photosensitive photoresist material, OFPR-8600manufactured by Tokyo Ohka Kogyo Co., Ltd., as the photoresist material.The photoresist material is applied and then heated by pre-baking withmicrowaves to remove moisture, thereby forming the photoresist layer 34on the silicon oxide film 33A.

In the step of patterning the photoresist, the photoresist layer 34 ismasked so that a portion for forming each silicon oxide film aperture 36is opened, and then subjected to exposure and development. Then, thephotoresist layer 34 is removed from a portion corresponding to eachsilicon oxide film aperture 36 to simultaneously form the manyphotoresist layer apertures 35 in each of which the silicon oxide film33A is exposed, as shown in FIGS. 13 and 14. As shown in FIG. 13, 3×5photoresist layer apertures 35 are formed on the silicon substrate 21 sothat 15 vibrating elements 20 are simultaneously formed through thesteps described below.

In the first etching step, the silicon oxide film 33A exposed from eachphotoresist layer aperture 35 is removed. In the first etching step, inorder to maintain the smoothness of the interface of the siliconsubstrate 21, a wet etching method is used for removing only the siliconoxide film 33A. However, the etching method is not limited to this, andappropriate etching, such as ion etching or the like, may be used.

In the first etching step, for example, an ammonium fluoride solution isused as an etchant for removing the silicon oxide film 33A to form thesilicon oxide film apertures 36. As shown in FIGS. 15 and 16, as aresult, the first main surface 21-1 of the silicon substrate 21 ispartially exposed to the outside. In the first etching step, whenetching is performed over a long time, a side etching phenomena occurs,in which etching proceeds from the sides of the silicon oxide filmapertures 36. Therefore, the etching time is preferably preciselycontrolled so that etching is stopped at the end of etching of thesilicon oxide film 33A.

In the second etching step, the etched recesses 37 are formed in theexposed portions of the first main surface 21-1 of the silicon substrate21, the exposed portions being exposed to the outside through therespective silicon oxide film apertures 36. In the second etching step,the silicon substrate 21 is etched to leave a depth corresponding to thethickness of the vibrator parts 23 by crystal anisotropic wet etchingusing the property that the etching rate depends on the crystalorientation of the silicon substrate 21.

The second etching step uses, for example, a TMAH (tetramethylammoniumhydroxide), KOH (potassium hydroxide), or EDP(ethylenediamine-pyrocatechol-water) solution, as the etchant.Specifically, the second etching step uses a 20% TMAH solution as theetchant, for increasing the etching ratio of the silicon oxide films 33Aand 33B on the front and back surfaces. The etching is performed for 6hours with the etchant kept at a temperature of 80° C. under stirring toform the etched recesses 37 shown in FIGS. 17 and 18.

In the second etching step, the etching is performed so that a (110)orientation plane at an angle of about 55° with respect to a (100) planeappears using the property of the silicon substrate 21 used as a basematerial that the etching rate of the side 21-3 is lower than that ofthe first and second main surfaces 21-1 and 21-2. As a result, theetched recesses 37 are formed so that the opening size of each recess 37gradually decreases at an inclination angle of about 55° from theopening to the bottom, and an etched inclined surface 133 at aninclination angle of about 55° is formed at the inner wall of eachetched recess 37.

Each of the etched recesses 37 constitutes a diaphragm part 38 forforming each vibrator part 23 by the outer shape cutting step which willbe described below. As shown in FIG. 17, each of the etched recesses 37has an aperture having a length dimension t8 and a width dimension t9.As shown in FIG. 19, each of the etched recesses 37 has a depthdimension t10 and forms a space having a trapezoidal sectional shape inwhich the opening size gradually decreases from the first main surface21-1 to the second main surface 21-2.

Each of the etched recesses 37 is formed to have the inner peripheralwall inclined at an inclination angle θ of 55° toward the bottomthereof, as described above. Each of the diaphragm parts 38 is definedby the width dimension t6 and the length dimension t5 of the vibratorpart 23 and the width dimension t7 (refer to FIGS. 36 and 37) of theoutside groove 39 formed by cutting the silicon substrate 21 along theperiphery of the vibrator part 23. The width dimension t7 of the outsidegroove 39 is determined by the equation, depth dimension t10×1/tan 55°.

Therefore, in each of the etched recesses 37, the opening widthdimension t9 which defines the width of the diaphragm part 38 isdetermined by the equation, (depth dimension t10×1/tan 55°)×2+t6 (widthdimension of the vibrator part 23)+2×t7 (width dimension of the outsidegroove 39). In each of the etched recesses 37, when t10 is 200 μm, t6 is100 μm, and t7 is 200 μm, the width dimension t9 of the opening is 780μm.

Like in the width direction, in the length direction, each of the etchedrecesses 37 is formed by the above-described second etching step to havean inclined surface at an inclination angle of 55° on the innerperipheral wall. Therefore, in each of the etched recesses 37, thelength dimension t8 which defines the length of the diaphragm part 38 isdetermined by the equation, (depth dimension t10×1/tan 55°)×2+t5 (lengthdimension of the vibrator part 23)+t7 (width dimension of the outsidegroove 39). In each of the etched recesses 37, when t10 is 200 μm, t5 is2.5 mm, and t7 is 200 μm, the length dimension t8 of the opening is 2980μm.

(Electrode Forming Step (Deposition))

In the above-described step of forming the etched recesses, therectangular diaphragm parts 38 each having a predetermined thickness areformed between the bottoms of the respective etched recesses 37 and thesecond main surface 21-2 of the silicon substrate 21. The diaphragmparts 38 constitute the vibrator parts 23 of the respective vibratingelements 20. After the etched recesses 37 are formed, the second mainsurface sides of the diaphragm parts 38 are used as processed surfacesin the electrode forming step.

In the electrode forming step, the electrode layers are formed by, forexample, a magnetron sputtering apparatus, on a portion of the secondmain surface 21-2, which corresponds to each etched recess 37, throughthe silicon oxide film 33B. The electrode forming step, as shown in FIG.20, includes the steps of forming the first electrode layer 40 forforming the reference electrode layer 27 on the silicon oxide film 33B,forming a piezoelectric layer 41 for forming the piezoelectric thin filmlayer 28, and forming the second electrode layer 42 for forming thedriving electrode layer 29 and the detection electrodes 30.

In the process for producing the vibrating elements, a step of forming aconductor layer for forming the leads 31 and the terminal parts 25 inthe respective formation regions on each base part 22 is performed inconformity with the step of forming the first electrode layer 40 and thestep of forming the second electrode layer 42 on each vibrator part 23.

The step forming the first electrode layer includes a step of forming atitanium thin film layer by sputtering titanium over the entire surfaceof the silicon oxide film 33B within a region corresponding to eachvibrator part 23, and a step of forming a platinum layer on the titaniumthin film layer by sputtering platinum to form the first electrode layer40 including the two layers. In the step of forming the titanium thinfilm layer, the titanium thin film layer is deposited to a thickness of50 nm or less (for example, 5 nm to 20 nm) on the silicon oxide film 33Bunder the sputtering conditions including, for example, a gas pressureof 0.5 Pa and a RF (radio frequency) power of 1 kw. In the step offorming the platinum layer, the platinum thin film layer is deposited toa thickness of about 200 nm on the titanium thin film layer under thesputtering conditions including, for example, a gas pressure of 0.5 Paand a RF power of 0.5 kW.

In the first electrode layer 40, the titanium thin film layer has thefunction to improve the adhesion to the silicon oxide film 33B, and theplatinum layer functions as a satisfactory electrode. In the step offorming the first electrode layer, as described above, the conductorlayer for forming the first lead 31A and the first terminal part 25A,which extend from each diaphragm part 38 to the formation regions of thecorresponding base part 22, is formed at the same time as the formationof the first electrode layer 40.

In the step of forming the piezoelectric film layer, the piezoelectricfilm layer 41 is deposited to a predetermined thickness by sputtering,for example, lead zirconate titanate (PZT) over the entire surface ofthe first electrode layer 40. In the step of forming the piezoelectricfilm layer, the piezoelectric film layer 41 including a PZT layer isdeposited to a thickness of about 1 μm on the first electrode layer 40using Pb_((1-x))(Zr_(0.53)Ti_(0.47))_(3-y) oxide as a target under thesputtering conditions including, for example, a gas pressure of 0.7 Paand a RF power of 0.5 kW. Also, the piezoelectric film layer 41 iscrystallized by baking heat treatment in an electric oven. The bakingtreatment is performed at 700° C. in an oxygen atmosphere for 10minutes. The piezoelectric film layer 41 is formed to cover a portion ofthe electrode layer extended from the first electrode layer 41 to theformation region on each base part 22.

In the step of forming the second electrode layer, a platinum layer isformed by sputtering platinum over the entire surface of thepiezoelectric film layer 4 to form the second electrode layer 42. Theplatinum thin film layer is deposited to a thickness of about 200 nm onthe piezoelectric film layer 41 under the sputtering conditionsincluding, for example, a gas pressure of 0.5 Pa and a RF power of 0.5kW.

(Electrode Forming Step (Patterning))

Next, the step of patterning the second electrode layer 42 formed as anuppermost layer is performed. In the step of pattering the secondelectrode layer, the driving electrode layer 29 and the pair of thedetection electrodes 30R and 30L each having a predetermined shape areformed as shown in FIGS. 21 and 22.

As described above, the driving electrode layer 29 serves as anelectrode for applying a predetermined drive voltage for driving eachvibrator part 23 and is formed with a predetermined width in a centralregion of each vibrator part 23 in the width direction to extent oversubstantially the entire region in the length direction thereof. Thedetection electrodes 30 are electrodes for detecting the Coriolis' forceproduced in each vibrator part 23 and are formed in parallel on bothsides of the driving electrode layer 29 to be insulated from each otherover substantially the entire region in the length direction.

In the step of patterning the second electrode layer, the secondelectrode layer 42 is subjected to photolithographic treatment to formthe driving electrode layer 29 and the detection electrodes 30 on thepiezoelectric film layer 41, as shown in FIG. 21. In the step ofpattering the second electrode layer, a resist layer is formed onportions corresponding to the driving electrode layer 29 and thedetection electrodes 30, and unnecessary portions of the secondelectrode layer 42 are removed by, for example, ion etching or the like.Then, the resist layer is removed to pattern the driving electrode layer29 and the detection electrodes 30. The step of patterning the secondelectrode layer is not limited to this, and the driving electrode layer29 and the detection electrodes 30 may be formed using an appropriateconductor layer forming step used in a semiconductor process.

As shown in FIG. 21, the driving electrode layer 29 and the detectionelectrodes 30 are formed so that the tips thereof are disposed at thesame position in the length direction, and also the root parts to bedisposed at the root of each vibrator part 23 are disposed at the sameposition 43 in the length direction. In the step of pattering the secondelectrode layer, wider lead connection parts 29-1, 30R-1, and 30L-1 areformed by pattering integrally with the base ends of the drivingelectrode layer 29 and the detection electrodes 30R and 30L,respectively, which have the root parts disposed at the same position 43in the length direction.

In the step of patterning the second electrode layer, the secondelectrode layer 42 is patterned to form the driving electrode layer 29,for example, having a length dimension t12 of 2 mm and a width dimensiont13 of 50 μm. Furthermore, as shown in FIG. 21, the first and seconddetection electrodes 30R and 30L each having a width dimension t14 of 10μm are formed by patterning so that the driving electrode layer 29 isheld therebetween with a space t15 of 5 μm between the driving electrodelayer 29 and each detection electrode 30. Also, the lead connectionparts 29-1, 30R-1, and 30L-1 each having a length dimension of 50 μm anda width dimension of 50 μm are formed by pattering. The dimension valuesof the driving electrode layer 29 and the detection electrodes 30 arenot limited to the above-described values, and these are appropriatelyformed within a range which permits the formation on the second mainsurface of each vibrator part 23.

Then, in the step of pattering the piezoelectric film layer 41, thepiezoelectric thin film layer 28 having a predetermined shape is formedas shown in FIGS. 23 and 24. The piezoelectric thin film layer 28 isformed by patterning the piezoelectric film layer 41, leaving an arealarger than the driving electrode layer 29 and the detection electrodes30. The piezoelectric thin film layer 28 is formed to have a widthslightly smaller than that of each vibrator part 23 and extend from thebase end to a vicinity of the tip thereof.

In the step of pattering the piezoelectric film layer, a resist layer isformed on a region of the piezoelectric film layer 41, which correspondsto the piezoelectric thin film layer 28, by photolithographic treatment.Then, unnecessary portions of the piezoelectric film layer 41 areremoved by wet etching or the like, for example, using a fluoronitricacid solution, and the resist layer is removed to form the piezoelectricthin film layer 28, as shown in FIGS. 23 and 24. Although, in thisembodiment, the piezoelectric film layer 41 is etched by wet etching,the etching method is not limited to this. For example, thepiezoelectric thin film layer 28 may be formed by an appropriate method,for example, ion etching, reactive ion etching (RIE), or the like.

As shown in FIG. 23, in the step of pattering the piezoelectric filmlayer, the piezoelectric thin film layer 28 is formed to havesubstantially the same root part as those of the driving electrode layer29 and the detection electrodes 39 at the root position 43 correspondingto the root of each vibrator part 23. Furthermore, a terminal receivingpart 28-1 is integrally formed by patterning at the base end of thepiezoelectric thin film layer 28 so as to have an area slightly lagerthan that of the lead connection parts 29-1, 30R-1, and 30L-1 of thedriving electrode layer 29 and the detection electrodes 30.

In the step of patterning the piezoelectric film layer, thepiezoelectric thin film layer 28 is formed by patterning to have alength dimension t18 of 2.2 mm which is slightly larger than that of thedriving electrode layer 29 and the detection electrodes 30, and have awidth dimension t19 of 90 μm. The terminal receiving part 28-1 formed bypatterning at the base end of the piezoelectric thin film layer 28 has aperipheral portion having a width dimension of 5 μm around the leadconnection parts 29-1, 30R-1, and 30L-1 of the driving electrode layer29 and the detection electrodes 30. The dimension values of thepiezoelectric thin film layer 28 are not limited to the above-describedvalues, and the piezoelectric thin film layer 28 is appropriately formedto have an area larger than that of the driving electrode layer 29 andthe detection electrodes 30 within a range permitting the formation onthe second main surface 23-2 of each vibrator part 23.

Furthermore, in the step of pattering the first electrode layer, thefirst electrode layer 40 is patterned by the same step as that forpatterning the second electrode layer to form the reference electrodelayer 27, as shown in FIGS. 25 and 26. In this step, a resist layer isformed on a region corresponding to the reference electrode layer 27,and unnecessary portions of the first electrode layer 40 are removed by,for example, ion etching or the like. Then, the resist layer is removedto form the reference electrode layer 27. The step of patterning thefirst electrode layer is not limited to this step, and the referenceelectrode layer 27 may be formed using an appropriate conductor layerforming step used in a semiconductor process.

In the step of patterning the first electrode layer, the referenceelectrode layer 27 is formed on the second main surface of each vibratorpart 23 to have a width slightly smaller than that of the second mainsurface of each vibrator part 23 and larger than that of thepiezoelectric thin film layer 28. As shown in FIG. 25, the base end ofthe reference electrode layer 27 is formed to have substantially thesame shape as the driving electrode layer 29, the detection electrodes30, and the piezoelectric thin film layer 28 at the root position 43corresponding to the root of each vibrator part 23. In this step, thefirst lead 31A and the first terminal part 25A at the end of the firstlead 31A are integrally formed by patterning in a formation region onthe base part 22 so as to be extended sideward from the base end.

In the step of pattering the first electrode layer, the referenceelectrode layer 27 is formed to have a length dimension t20 of 2.3 mmand a width dimension t21 of 94 μm, and also has a peripheral portionhaving a width dimension of 5 μm around the piezoelectric thin filmlayer 28. In the step of patterning the first electrode layer, thedimension values of the reference electrode layer 27 are not limited tothe above-described values, and the reference electrode layer 27 may beformed within a range which permits the formation on the second mainsurface of each vibrator part 23.

(Step of Forming Planarizing Layer)

In the process for manufacturing the vibrating elements, the leadconnection parts 29-1, 30R-1, and 30L-1 of the driving electrode layer29 and the detection electrodes 30, and the terminals parts 25B to 25Dare formed in the respective formation regions on each base part 22through the above-described steps, and also leads 31B to 31D to beconnected to the respective terminal parts 25 are formed. In order tosmoothly connect the leads 31B to 31D to the lead connection parts 29-1,30R-1, and 30L-1, the planarizing layer 24 is formed as shown in FIGS.27 and 28.

The leads 31B to 31D for connecting the lead connection parts 29-1,30R-1, and 30L-1 to the terminal parts 25B to 25D, respectively, areformed to cross over the ends of the terminal receiving part 28-1 of thepiezoelectric thin film layer 28 and the reference electrode layer 27and extend in the respective formation regions on each base part 22. Asdescribed above, the piezoelectric thin film layer 28 is formed bypatterning the piezoelectric thin film layer 41 using wet etching, andthus the edge of an etched portion is inverse-tapered toward the secondmain surface 21-2 of the silicon substrate 21 or vertically stepped.Therefore, when the leads 31B to 31D are formed directly in therespective formation regions on each base part 22, disconnection mayoccur at the stepped portion. Also, it may be necessary to maintaininsulation between the first lead 231A and the leads 31B to 31D extendedin the respective formation regions on each base part 22.

In the step of forming the planarizing layer, a resist layer formed in aformation region on each base part 22 is patterned by photolithographictreatment to cover the lead connection parts 29-1, 30R-1, and 30L-1 andthe first lead 31A. The resist layer pattern is cured by heat treatmentat, for example, about 160° C. to 300° C., to form the planarizing layer24. In this step, the planarizing layer 24 is formed to have a widthdimension of t24 of 200 μm, a length dimension t25 of 50 μm, and athickness dimension of 2 μm (exaggerated in FIG. 28). The step offorming the planarizing layer is not limited to this step, and theplanarizing layer 24 may be formed using an appropriate insulatingmaterial in an appropriate resist layer forming step performed in asemiconductor process or the like.

(Step of Forming Wiring Layer)

Next, the step of forming the wiring layer is performed for forming thesecond to fourth terminal parts 25B to 25D and the second to fourthleads 31B to 31D in the respective formation regions on each base part22. In the step of forming the wiring layer, a photosensitivephotoresist layer is formed over the entire region of a formation regionon each base part 22, and then subjected to photolithographic treatmentto form a pattern of apertures corresponding to the second to fourthterminal parts 25B to 25D and the second to fourth leads 31B to 31D.Furthermore, a conductor layer is formed in each of the apertures bysputtering to form the wiring layer. In this step, after predeterminedconductor portions are formed, the photoresist layer is removed to formthe second to fourth terminal parts 25B to 25D and the second to fourthleads 31B to 31D, as shown in FIGS. 29 and 30.

In the step of forming the wiring layer, a titanium layer or an aluminalayer is formed as an underlying layer for improving the adhesion to thesilicon oxide film 33B, and then a low-cost copper layer having lowelectric resistance is formed on the titanium layer. In this embodiment,for example, the titanium layer is formed to a thickness of 20 nm, andthe copper layer is formed to a thickness of 300 nm. The step of formingthe wiring layer is not limited to this step, and the wiring layer maybe formed by, for example, any wiring pattern forming techniquegenerally used in a semiconductor process.

(Step of Forming Insulating Protective Layer)

Then, the step of forming the insulating protective layer is performedfor forming the insulating protective layer 45 including three layersover the main surfaces of each base part 22 on which the terminals 25and the leads 31 have been formed by the above-described steps and eachvibrator part 23 on which the electrode layers and the piezoelectricthin film layer 28 have been formed. The step of forming the insulatingprotective layer includes the steps of forming a resist layer,patterning the resist layer, forming a first alumina layer, forming asilicon oxide layer, forming a second alumina layer, and removing theresist layer.

In the step of forming the insulating protective layer, the steps offorming the resist layer and pattering the resist layer are performed toform a resist layer 44 having an aperture in a region corresponding tothe insulating protective layer 45 on the second main surface of thesilicon substrate 21, as shown in FIG. 31. In the step of forming theresist layer, a photosensitive resist agent is applied over the entiresurface of the silicon substrate 21 to form the resist layer 44. In thestep of patterning the resist layer, the resist layer 44 is subjected tophotolithographic treatment to form an aperture corresponding to aformation region of the insulating protective layer 45, thereby formingan insulating protective layer formation aperture 44A. Although notshown in the drawing, the resist layer 44 is left in circular portionscorresponding to the respective terminal parts 25.

In the step of forming the insulating protective layer, the firstalumina layer 46, the silicon oxide layer 47, and the second aluminalayer 48 are laminated by sputtering, and unnecessary portions of thesputtered films are removed together with the resist layer 44 to leave athree layer-structure sputtered layer in the insulating protective layerformation aperture 44A of the resist layer 44. Namely, the desiredinsulating protective layer 45 is formed by a so-called liftoff method.FIGS. 32 to 34 show only the sputtered films formed in the insulatingprotective layer formation aperture 44A. However, of course, thesputtered films are formed on the resist layer 44 having the insulatingprotective layer forming aperture 44A, and these sputtered films aresimultaneously removed together with the resist layer 44 in the resistlayer removing step.

In the step of forming the first alumina layer, the first alumina layer46 is formed by sputtering alumina in the insulating protective layerformation aperture 44A, as shown in FIG. 32. The first alumina layer 46is formed to have a thickness dimension t26 of about 50 nm and functionsas an underlying metal layer for improving the adhesion to the siliconsubstrate 21 and the driving electrode layer 29 or the detectionelectrodes 30 within the insulating protective layer formation aperture44A, as described above.

In the step of forming the silicon oxide layer, the silicon oxide layer47 is formed on the first alumina layer 46 by sputtering silicon oxide,as shown in FIG. 33. In this step, since the lower limit of argonpressure for discharge in a sputtering vessel is 0.35 Pa, the siliconoxide layer 47 with a high density is formed by sputtering silicon oxideat an argon pressure set at 0.4 Pa slightly higher than the lower limit.The silicon oxide layer 47 formed in this step exhibits a sufficientinsulating protective function because the thickness thereof is at leasttwice that of the driving electrode layer 29 and the detectionelectrodes 30, and the thickness dimension t27 is 1 μm or less within aregion in which burr occurs at a low rate in the liftoff method.Specifically, the silicon oxide layer 47 is formed with a thicknessdimension t27 of 750 nm.

In the step of forming the second alumina layer, as shown in FIG. 34,the second alumina layer 48 is formed by sputtering alumina over theentire surface of the silicon oxide layer 47. The second alumina layer48 is formed to have a thickness dimension t28 of about 50 nm, forimproving the adhesion to a resist layer to be formed in the outer shapegrooving step which will be described below, thereby preventing thesilicon oxide layer 47 from being damaged by an etching agent.

(Outer Shape Grooving Step)

Next, as shown in FIG. 34, an etching stop layer 70 is formed on thefirst main surface 21-1 of the silicon substrate 21. The etching stoplayer 70 functions to suppress the occurrence of a defective shape inwhich plasma concentration occurs on the first main surface 21-1 to failto form a predetermined edge shape in the step of forming an outsidegroove in the silicon substrate 21, which will be described below. Inthe step of forming the etching stop layer, for example, a silicon oxidelayer is formed to a thickness of about 500 nm by sputtering over theentire surface of the first main surface 21-1 of the silicon substrate21.

In the outer shape grooving step, the outside groove 39 is formed topass through the diaphragm part 38, for forming the periphery of eachvibrator part 23. In this step, as shown in FIGS. 35 to 37, the outsidegroove 39 is formed as a U-shaped through groove from the second mainsurface 21-2 of the silicon substrate 21, which faces the diaphragmparts 38, so as to surround each vibrator part 23 and extend from thestart end 39A at one of the sides of the root position 43 of eachvibrator part 23 to the finish end 39B at the other aide of the rootposition 43. As described above, the outside groove 39 is formed to havethe width dimension t7 of 200 μm.

Specifically, the outer shape grooving step includes a first etchingstep of removing a U-shaped portion in a predetermined form of thesilicon oxide film 33B to expose the second main surface 21-2 of thesilicon substrate 21, and a second etching step of forming the outsidegroove 39 in the exposed portion of the silicon substrate 21.

In the first etching step, a photosensitive photoresist layer is formedover the entire surface of the silicon oxide film 33B and subjected tophotolithographic treatment to form a U-shaped aperture patternsurrounding the formation region on the electrode layers, the aperturepattern having an opening size which is the same as the outer dimensionof each vibrator 23. In this step, the silicon oxide film 33B exposedthrough the aperture pattern is removed by ion etching. Although, in thefirst etching step, the silicon oxide film 33B may be removed in aU-shaped form by, for example, wet etching, ion etching is preferred inview of the occurrence of dimensional error due to side etching.

In the second etching step, the remaining silicon oxide film 33B is usedas a resist film (etching protective film). In this step, for example,the silicon substrate 21 is subjected to reactive ion etching, forachieving a proper etching ratio to the resist film (silicon oxide film33B) and forming a high-precision vertical surface as the outerperiphery of each vibrator part 23.

In the second etching step, a reactive ion etching (RIE) apparatushaving the function to produce inductively coupled plasma (ICP) is usedfor producing a high-density plasma. This step uses a Bosch (BoschCorp.) process in which an etching step of introducing SF₆ gas to anetching portion and a step of introducing C₄F₈ gas to form a protectivefilm for protecting the outer periphery of the etched portion arerepeated. As a result, the outside groove 39 having a vertical innerwall is formed in the silicon substrate 21 at a rate of about 10 μm perminute.

After the second etching step, a step of removing the etching stop layer70 formed on the first main surface 21-1 of the silicon substrate 21 ispreformed. In this step, the etching stop layer 70 composed of siliconoxide is removed by, for example, wet etching with ammonium fluoride.Since, in the step of removing the etching stop layer, the insulatingprotective layer 45 is also removed by removing the photoresist layerformed in the step of forming the outside groove, the photoresist layeris removed after removing the etching stop layer 70.

(Polarization Step)

Then, the polarization step is performed for simultaneously polarizingthe piezoelectric thin films 28 formed on the respective vibratingelements 20 on the silicon oxide substrate 21. The polarization isperformed using Cu wiring as polarization wiring. After thepolarization, the Cu wiring is easily dissolved by wet etching andremoved without damage to the vibrating elements 20. The polarizationwiring is not limited to the Cu wiring, and an appropriate conductorexhibiting the above-described function may be used for the wiring.

The Cu wiring is formed by a liftoff method in which a resist layerpattern having an aperture with a predetermined shape is formed on thesecond main surface 21-2 of the silicon substrate 21 by, for example,photolithographic treatment, a Cu layer is deposited by sputtering, andthe Cu layer is removed from unnecessary portions together with theresist layer. For example, the Cu wiring has a width dimension of 30 μmor more and a thickness of about 400 nm, for securing conduction duringthe polarization.

The polarization step is effectively performed by simultaneouslyconnecting the vibrating elements 20 to an external power supply throughapplication-side pads formed in the Cu wiring and ground-side pads. Inthe polarization step, each pad is connected to the external powersupply by, for example, were bonding, and polarization is performed byconduction at 20 V for 20 minutes. The polarization is not limited tothis step, and the polarization may be performed by an appropriateconnection method under proper polarization conditions.

(Step of Forming Gold Bumps)

Next, the step of forming the gold bumps is performed. As descriedabove, each of the vibrating elements 20 is mounted on the supportsubstrate 2, and thus the gold bump 26 is formed on each terminal part25. In the step of forming the gold bumps 26, a stud bump having apredetermined shape is formed by pressing a gold wire bonding tool toeach terminal part 25. In this step, if required, dummy bumps are alsoformed on each base part 22. The gold bumps 26 may be formed by anothermethod, for example, a plating bump method which will be describedbelow.

The plating bump method includes a step of forming a plating resistlayer 62 having a predetermined aperture 61 on each terminal part 25 asshown in FIG. 38A, a step of plating gold to grow a gold plating layer26 to a predetermined height in each aperture 61 as shown in FIG. 38B,and a step of removing the resist layer 62. In the step of forming thegold bumps, the thickness (height) of the gold bumps 26 is limited byplating conditions, and the gold bumps 26 having a predetermined heightmay not be formed. In the step of forming the gold bumps, when thedesired gold bumps 26 are not obtained by first plating, second platingmay be performed again using the first plating layer as an electrode toform so-called stepped gold bumps 26.

The method for the step of forming the gold bumps 26 is not limited tothe above-described methods, and bumps may be formed by, for example,vapor deposition, transfer, or the like which is carried out in asemiconductor process. Although not described in detail, in the processfor manufacturing the vibrating elements, a so-called bump metalunderlayer of TiW, TiN, or the like is formed for improving the adhesionbetween the gold bumps 26 and the terminal parts 25.

(Cutting Step)

Next, the cutting step is performed for cutting the silicon substrate 21into the respective vibrating elements 20. In the cutting step, aportion corresponding to each base part 22 is cut with, for example, adiamond cutter or the like to cut into the respective vibrating elements20. In this step, cutting grooves are formed by a diamond cutter, andthen the silicon substrate 21 is cut by bending. The cutting step may beperformed by a grindstone or polishing using plane orientations of thesilicon substrate 21.

By using the above-descried process for manufacturing the vibratingelements, the number of the vibrating elements obtained from the siliconsubstrate (wafer) 21 may be significantly increased, as compared with,for example, a case in which vibrator parts are integrally formed on theadjacent sides of a common base part 22 to produce a two-axis integratedvibrating element for obtaining detection signals in two axisdirections.

(Mounting Step)

Each of the vibrating elements 20 manufactured by the above-descriedsteps is mounted on the first main surface 2-1 of the support substrate2 by the surface mounting method using the second main surface 21-2 ofthe silicon substrate 21 as the mounting surface. In the vibratingelement 20, the gold bumps 26 provided on the respective terminal parts25 are aligned with the corresponding lands 4 on the support substrateside. In this case, as described above, the alignment marks 32 of eachvibrating element 20 are read, and then the vibrating element 20 ispositioned by the mounting machine with high positional precision anddirectional precision.

Each vibrating element 20 is mounted on the first main surface 2-1 ofthe support substrate 2 by ultrasonically welding the gold bumps 26 tothe corresponding lands 4 while the vibrating element 20 is pressed onthe support substrate 2. The IC element 7 and the electronic components8 are mounted on the first main surface 2-1 of the support substrate 2,and each vibrating element 20 is subjected to the adjustment step whichwill be describe below. Then, the cover member 15 is attached tocomplete the vibrating gyrosensor 1.

As described above, according to this embodiment, a plurality ofvibrating elements 20 is simultaneously produced on the siliconsubstrate 21, the vibrating elements 20 each including the vibrator part23 integrally formed with the base part 22, and then the siliconsubstrate 21 is cut into the respective vibrating elements. Then, thefirst and second vibrating elements 20X and 20Y having the same shapeare mounted on two axes crossing at an angle of 90° on the first mainsurface 2-1 of the support substrate 2 to produce the vibratinggyrosensor 1 for obtaining detection signals in the two axes.

(Adjustment Step)

In the step for manufacturing the vibrating elements, as describedabove, the vibrator part 23 of each vibrating element 20 is preciselycut off from the silicon substrate 21 by etching using inductivelycoupled plasma. However, it may be difficult to form each vibrator part23 symmetric with respect to the emission center line of the plasmadepending on the conditions such as material yield and the like.Therefore, variations may occur in the shape of each vibrator part 23due to a positional shift of each vibrating element 20, various processconditions, or the like. For example, when the vibrator part 23 of eachvibrating element 20 is formed to have a trapezoidal or parallelogramsectional shape, the vibrator part 23 performs a vibration operationinclined toward a small-mass side from the center axis direction ofvertical vibration, as compared with a vibrator part 23 having a normalrectangular sectional shape.

Therefore, the adjustment step is performed for correcting a vibrationstate by laser-polishing a predetermined position on a large-mass sideof each vibrator part 23. In the adjustment step, since it may bedifficult to directly observe the sectional shape of each vibrator part23 having a small sectional shape, variations in the sectional shape ofthe vibrator part 23 are observed by a method in which the vibrator part23 of each of the cut vibrating elements 20 is vibrated at apredetermined longitudinal resonance frequency to compare the magnitudesof right and left detection signals. In the adjustment step, when adifference occurs between the right and left detection signals, thevibrator part 23 is partially laser-cut on the side outputting a smallerdetection signal.

For example, before adjustment, oscillation output G0 of the oscillatorcircuit 71 is applied to the driving electrode layer 29 to vibrate thevibrating element 20 in a longitudinal resonance state, as shown in FIG.39A. In the adjustment step, the detection signals Gl0 and Gr0 outputfrom the pair of the detection electrodes 30L and 30R are combined bythe adding circuit 72, and the addition signal is returned to theoscillator circuit 71. Then, on the basis of the detection signals Gl0and Gr0 obtained from the detection electrodes 30L and 30R, theoscillation frequency of the oscillator circuit 71 is measured as alongitudinal resonance frequency f0, and a difference between thedetection signals Gl0 and Gr0 is measured as a differential signal.

In the adjustment step, as shown in FIG. 39B, the oscillation output Glof the oscillator circuit 71 is applied to the detection electrode 30Lto drive the vibrating element 20 in a transverse resonance state. Inthis step, the detection signal Gr-1 output from the detection electrode30R is returned to the oscillator circuit 71, and on the basis of thedetection signals Gr-1, the oscillation frequency of the oscillatorcircuit 71 is measured as a transverse resonance frequency f1. Since thetransverse resonance frequency f1 obtained from the detection signalGr-1 is equal to the transverse resonance frequency f2 obtained from thedetection signal Gl-1, the transverse resonance frequency may bemeasured by connecting to any one of the detection electrodes 30L and30R.

Furthermore, as shown in FIG. 39C, the oscillation output G2 of theoscillator circuit 71 is applied to the detection electrode 30R to drivethe vibrating element 20 in a transverse resonance state. In this step,the detection signal Gl-2 output from the detection electrode 30L isreturned to the oscillator circuit 71, and on the basis of the detectionsignals Gl-2, the oscillation frequency of the oscillator circuit 71 ismeasured as a transverse resonance frequency f2. In the adjustment step,a difference between the longitudinal resonance frequency f0 and thetransverse resonance frequency f1 or f2 obtained by the measurement isused as a degree of detuning, and decision is made as to whether or notthe degree of detuning is within a predetermined range. Also, in theadjustment step, decision is made as to whether or not the differentialsignal detected by the detection electrodes 30L and 30R is within apredetermined range.

In the adjustment step, on the basis of the decision results of thedegree of detuning and the differential signal, an adjustment positionof the vibrator part 23 is determined from the magnitudes thereof, andthe portion of the vibrator part 23 is polished by laser irradiation.The adjustment step is performed by the same measurement and leaserprocessing as described above until the decision results of the degreeof detuning and the differential signal reach the target values.

The adjustment step uses a laser device having a controllable spotdiameter and emitting a laser at a wavelength of 532 nm. In theadjustment step, for example, an edge between a side and the first mainsurface 23-1 is adjusted by irradiating a proper portion in the lengthdirection with the laser. Since, in each of the vibrating elements 20,changes in both a frequency difference and a detection signal balance bylaser irradiation adjustment decrease from the base end to the tip ofthe vibrator part 23, the base end side may be roughly adjusted, and thetip side may be finely adjusted.

Since the adjustment step is performed for the vibrating element 20mounted on the support substrate 2, re-adjustment after mounting, whichis preformed when the adjustment is performed before mounting, may notbe performed, thereby increasing the productivity of the vibratinggyrosensor 1. In this case, a region irradiated by the adjustment laseris on the upper surface 23-2 side of the vibrator part 23, and thusadjustment workability after mounting is excellent. Since thepiezoelectric layer and the electrode layers are not formed on the uppersurface 23-2 of each vibrator part 23, the influences of the adjustment,such as a change in the characteristics of the piezoelectric thin filmlayer 28, a change in the polarization state, and the like due to theheat generated by laser processing, may be prevented as much aspossible.

In the vibrating gyrosensor 1, when an AC voltage at a predeterminedfrequency is applied to the driving electrode layer 29 in each vibratingelement 20 from the corresponding driving detector circuit part 50, thevibrator part 23 vibrates at a natural frequency. The vibrator part 23resonates at a longitudinal resonance frequency in the longitudinaldirection, which is the thickness direction, and also resonates at atransverse resonance frequency in the transverse direction, which is thewidth direction. The sensitivity of the vibrating element 20 increasesas a difference between the longitudinal resonance frequency and thetransverse resonance frequency, which refers to the degree of detuning,decreases. In the vibrating gyrosensor 1, as described above, when theouter periphery of each vibrator part 23 is formed with high precisionby crystal anisotropic etching and reactive ion etching, a satisfactorydegree of detuning is obtained.

In each of the vibrating elements 20, the characteristics of thelongitudinal resonance frequency are significantly affected by theprecision of the length dimension t5 of the vibrator part 23. Asdescribed above, at the root position 43 in each vibrating element 20,which defines the length dimension t5 of the vibrator part 23, when adeviation occurs between the (100) surface of the diaphragm part 38formed by crystal anisotropic etching and the (111) surface whichcorresponds to each etched inclined surface 133 at an angle of 55° andthe boundary line corresponding to a flat surface, the degree ofdetuning increases according to the amount of deviation.

Namely, in each of the vibrating elements 20, the amount of deviation iscaused by a positional shift between the resist film pattern formed onthe silicon oxide film 33B in crystal anisotropic etching and the resistfilm pattern formed in reactive ion etching. Therefore, for example,each of the vibrating elements 20 may be positioned using a both sidealigner capable of simultaneously observing the first and second mainsurfaces 21-1 and 21-2 of the silicon substrate 21. Alternatively,appropriate positioning patterns or marks may be formed on the first andsecond main surfaces 21-1 and 21-2 of the silicon substrate 21 so thateach vibrating element 20 is positioned by an alignment deviceperforming one-side alignment on the basis of these patterns or marks.This positioning method may be applied to the step of mounting eachvibrating element 20 on the support substrate 2.

When the amount of deviation in each vibrating element 20 is in a rangesmaller than about 30 μm, the longitudinal resonance frequency issubstantially the same as the transverse resonance frequency. Therefore,in each vibrating element 20, deterioration in the degree of detuningdue to the amount of deviation is substantially suppressed by an etchingstep with slightly higher precision, and the vibrating element ismanufactured without the above-descried positioning method using thealignment device.

(Effect of Pair of Vibrating Elements)

In the process for producing the vibrating elements, as described above,many vibrating elements 20 each having the vibrator part integrallyformed with the base part 22 are simultaneously formed on the siliconsubstrate 21, and the silicon substrate 21 is cut into the respectivevibrating elements 20. Therefore, the first vibrating element 20X andthe second vibrating element 20Y having the same shape are produced, andthe two vibrating elements 20X and 20Y are disposed at positions on twoaxes on a main surface of the support substrate 2 to produce thevibrating gyrosensor 1 for obtaining detection signals in the two axes.

In the process for manufacturing the vibrating elements, the number ofthe vibrating elements obtained from the silicon substrate (wafer) 21may be significantly increased, as compared with, for example, atwo-axis integrated vibrating element in which vibrator parts areintegrally formed on the adjacent sides of a common base part 22, forobtaining detection signals in two axis directions. FIG. 40 showscomparison of the number of the vibrating elements 20 obtained, each ofwhich includes the parts having the above-described dimensions and thenumber of the two-axis integrated vibrating elements obtained, each ofwhich has the same function as the vibrating elements 20.

FIG. 40 indicates that when a total of 60 vibrating elements 20(corresponding to 30 gyrosensors each including two vibrating elements)are produced using a 3-cm square silicon substrate, a total of 1200vibrating elements (corresponding to 600 gyrosensors 1) are producedusing a 4-inch diameter waver generally used in mass production by asemiconductor process, and a total of 4000 vibrating elements(corresponding to 2000 gyrosensors 1) are produced using a 5-inchdiameter waver. On the other hand, with respect to the two-axisintegrated vibrating elements, a total of 20 vibrating elements areproduced using a 3-cm square silicon substrate, a total of 300 vibratingelements are produced using a 4-inch diameter waver, and a total of 800vibrating elements are produced using a 5-inch diameter waver. In thevibrating elements 20, the material yield is significantly improved todecrease the cost.

In the vibrating gyrosensor 1, as described above, the first vibratingelement 20X and the second vibrating element 20Y for obtaining detectionsignals in two axes are positioned on the two axes at a right angle onthe support substrate 2. In the vibrating gyrosensor 1, consideration isgiven to the influence of the vibration operation of one of thevibrating elements on that of the other vibrating element, i.e., theoccurrence of interference between the two axes. FIG. 41 shows theresults of measurement of cross talk by turning over the first andsecond vibrating elements 20X and 20Y mounted in two directions on thesupport substrate 2.

In FIG. 41, type 1 is a gyrosensor in which first and second vibratingelements 20X-1 and 20Y-1 are mounted on the support substrate 2 so thatthe respective vibrator parts 23X-1 and 23Y-1 face each other, and therespective base parts 22X-1 and 22Y-1 are fixed at diagonal corners ofthe support substrate 2. Type 2 is a gyrosensor in which first andsecond vibrating elements 20X-2 and 20Y-2 are mounted on the supportsubstrate 2 so that the respective base parts 22X-2 and 22Y-2 are fixedat the same corner of the support substrate 2, and the respectivevibrator parts 23X-2 and 23Y-2 are extended along the side lines at aright angle. Type 3 is a gyrosensor in which a first vibrating element20X-3 is mounted on the support substrate 2 so that the base part 22X-3is fixed at one of the corners, and the vibrator part 23X-3 is directedtoward one of the corners adjacent to the corner of the base part 22X-3,and a second vibrating element 20Y-3 is mounted on the support substrate2 so that the base part 22Y-3 is fixed at the other of the cornersadjacent to the corner of the base part 22X-3, and the vibrator part23Y-3 is directed toward the first vibrating element 20X-3. As acomparative example, the figure also shows the cross talk value of theabove-described two-axis integrated vibrating element (type 0) 60. Theunit of cross talk is dbm (decibel/milliwatt).

FIG. 41 indicates that the cross talk value of the vibrating element 60of type 0 is −50 dbm, the cross talk value of the vibrating elements20X-1 and 20Y-1 of type 1 is −70 dbm, the cross talk value of thevibrating elements 20X-2 and 20Y-2 of type 2 is −60 dbm, and the crosstalk value of the vibrating elements 20X-3 and 20Y-3 of type 3 is −72dbm.

In the vibrating gyrosensor 1 of each of types 1 to 3 according to anembodiment of the present invention, an improvement of at least about−10 dbm is obtained regardless of the mounting state, as compared withthe two-axis integrated vibrating element 60 of type 0. In such avibrating gyrosensor 1, two independent vibrating elements 20 areprovided, and thus an interference signal between the detection signalsin the two axes is suppressed to about 1 mV. On the other hand, in thevibrating gyrosensor including the two-axis integrated vibratingelement, the interference signal between the detection signals in twoaxes is about 10 mV, thereby decreasing the detection performance.

In the vibrating gyrosensor 1 according to this embodiment of theinvention, when the first and second vibrating elements 20X and 20Y aremounted in the arrangement of type 1 on the support substrate 2, theleast interference between the two axes is produced. In the vibratinggyrosensor 1, the first and second vibrating element 20X and 20Y may bemounted at any portions of the support substrate 2. However, in view ofmounting of a small IC circuit element 7 and many electronic parts andextension of the wiring pattern, the base parts 22 are preferably fixedat the corners of the support substrate 2 as in the above-describedtypes because the mounting efficiency is most improved.

In the vibrating gyrosensor 1, the alignment marks 32 provided on eachvibrating element 20 are recognized when the first and second vibratingelement 20X and 20Y are mounted on the support substrate 2 using themounting machine so that the vibrating elements face each other on twoaxes crossing at a right angle. Also, in the vibrating gyrosensor 1, thevibrating elements 20 are preferably mounted on the support substrate 2so as not to cause a positional shift of each vibrator part 23. FIGS.42A and 42B are each a histogram showing the positional shifts of eachvibrating element 20 (distribution of shift angles with the centeraxis), in which the shift angle (degree) is shown on the abscissa, andquantity is shown on the ordinate. FIG. 42A shows mounting performed byrecognizing the alignment marks 32, and FIG. 48B shows mountingperformed by recognizing the outer shape of vibrating element 20. In thevibrating gyrosensor 1, as seen from FIGS. 42A and 42B, when a highdegree of recognition is performed using the alignment marks 32, thevibrating elements 20 are precisely mounted on the support substrate 2within a range in which variations in the occurrence of angular shift islow, and the shift angle is also low. Therefore, in the vibratinggyrosensor 1, each vibrating element 20 precisely and stably detectsmotion blurring.

In this embodiment, a pair of the vibrating elements 20X and 20Y ismounted on the first main surface 2-1 of the support substrate 2 so thatthe vibrator parts 23 are directed in the axial directions at a rightangle, for detecting angular velocities around two axes. Alternatively,at least tree vibrating elements may be mounted in different axialdirections on a common support substrate, for detecting angularvelocities around two axial directions. For example, three vibratingelements may be mounted on a common support substrate so that thevibrator parts thereof are disposed with an angular difference of 120°each.

Furthermore, two vibrating gyrosensors 1 according to this embodimentmay be prepared and mounted on surfaces perpendicular to each other in amain body device of a video camera or the like. In this case, angularvelocities around the three axial directions, i.e., the longitudinaldirection, transverse direction, and vertical direction, aresimultaneously detected.

(Cross Talk)

The operating frequency of each vibrating element 20 may be set in arange of several kHz to several hundreds kHz. In the two-axis angularvelocity sensor (vibrating gyrosensor 1), the magnitude of aninterference signal due to a frequency difference (fx−fy) was measuredwith changing operating frequencies (fx and fy) of the two vibratingelements 20X and 20Y. The results obtained are shown in FIG. 43. In FIG.43, the operating frequency difference (fx−fy) between the vibratingelements 20X and 20Y is shown on the abscissa, and an AC noise componentVo (magnitude between a high amplitude peak and a low amplitude peak ofan AC waveform indicating noise) superposed on the sensor output (DC) isshown on the ordinate. Here, the noise component Vo is referred to as“cross talk between axes”.

When the frequency difference (fx−fy) is less than 1 kHz, the cross talkvalue reaches 1500 mV_(pp) or more, and stable detection of an angularvelocity may be impossible. On the other hand, with a frequencydifference near 1 kHz, the cross talk value starts to decrease to 500mV_(pp). Specifically, with a frequency difference of 1.4 kHz, the crosstalk value is decreased to 200 mV_(pp), while with a frequencydifference of 2 kHz or more, the cross talk value is decreased to 100mV_(pp) or less. The results shown in FIG. 43 reveal that the cross talkbetween axes is significantly decreased by setting the frequencydifference (fx−fy) to 1 kHz or more. As a result of preparation of twotypes of samples for the vibrating elements 20X and 20Y having adifference of 1 kHz between the operating frequencies (fx and fy)thereof, a two-axis angular velocity sensor stably operating wasproduced.

Sample 1

First vibrating element 20X having an operating frequency of 37 kHz

Second vibrating element 20Y having an operating frequency of 36 kHz

Sample 2

First vibrating element 20X having an operating frequency of 40 kHz

Second vibrating element 20Y having an operating frequency of 39 kHz

FIG. 43 indicates that when the frequency difference (fx−fy) is set to 2kHz to 3 kHz, the influence of cross talk between the pair of vibratingelements 20X and 20Y is prevented. Therefore, the precision of thesensor output may be improved by driving the vibrating elements 20X and20Y with a frequency difference of 2 kHz or more.

Furthermore, the vibrating gyrosensor according to this embodiment maybe influenced by cross talk between the vibrating elements 20 and otherelectronic components (sensor and the like) provided on the main bodydevice side. However, a plurality of vibrating elements having differentoperation frequencies may be previously prepared so that a frequencycausing no influence may be selected as the driving frequency of eachvibrating element. Specifically, a plurality of vibrating elementshaving driving frequencies in a range of, for example, 35 kHz to 60 kHz,is prepared, and two vibrating elements having an operating frequencydifference of 1 kHz or more (preferably 2 kHz or more) are selected soas to avoid cross talk between the pair of vibrating elements andbetween the vibrating elements and other electronic components providedin the main body device.

The operating frequency of each of the vibrating elements 20X and 20Y isadjusted by adjusting the vibration properties such as a degree ofdetuning (frequency difference between the longitudinal resonancefrequency and the transverse resonance frequency) and a balance betweenright and left detection signals in the adjustment step for thevibrating elements 20, and then similarly adjusting the resonancefrequencies by laser trimming on the tip side of each vibrator part 23.

The vibrator part 23 of each vibrating element 20 is cantilevervibrator, and thus a resonance frequency is inversely proportional tothe square of the length of the cantilever beam as shown by theexpression below. In the expression, fn is the resonance frequency ofthe cantilever beam, E is the Young's modulus, I is the second moment ofarea of the cantilever beam, ρ is the density, A is the sectional areaof the beam, L is the length of the beam, and λ is the proportionalitycoefficient. Therefore, the rigidity and effective length of the beammay be decreased by laser-trimming the tip portion of each vibrator part23 to increase the resonance frequency of the beam.

$f_{n} = {{\frac{\lambda^{2}}{2\pi}\sqrt{\frac{E\; I}{p\; A\; L^{4}}}} = {\frac{\lambda^{2}}{2\pi}\sqrt{\frac{E\; I}{p\; A}}\frac{1}{L^{2}}}}$

On the other hand, in the adjustment of the resonance frequency, achange in the degree of detuning, which has previously been adjusted, ispreferably avoided. FIG. 44 is a diagram (graph) showing plots of dataobtained by measuring changes in the resonance frequency and degree ofdetuning with changes in the processing position of a cantilever beamhaving a laser processing depth of 11 μm and a length of 1.9 mm. FIG. 44indicates that when a position at a distance of 1.6 mm or more (⅘ ormore the overall length of the vibrator part 23) from the root of thebeam (base end of the vibrator part 23) is processed with a laser, theresonance frequency may be increased without changing the degree ofdetuning (93 Hz).

According to the above-descried results, as shown in FIG. 45, on theupper surface 23-1 of each vibrator part 23, a formation region of laserprocessed recesses (processing marks) 90 for resonance frequencyadjustment is provided at a distance of ⅘ or more the overall length ofthe vibrator part 23 from the root position thereof, and a formationregion 80 of laser processed recesses 8 for adjustment of the degree ofdetuning is provided at another portion.

As a result, the resonance frequencies of the vibrating elements 20X and20Y are adjusted to any different values without changing the degree ofdetuning, thereby easily avoiding cross talk between the axes. Also, theresonance frequency of each of the vibrating elements 20X and 20Y ispreferably adjusted in a frequency band region in which not only thecross talk between the vibrating elements but also the cross talkbetween the vibrating elements and other electronic components on themain body device have small influences.

Second Embodiment

In this embodiment, a mounting region of the IC circuit element 7 on thesupport substrate 2 is described.

As shown in FIG. 46, the IC circuit element 7 and other electroniccomponents 8 as well as the pair of vibrating elements 20 (20X and 20Y)are mixed-mounted on the support substrate 2. These components arefrequently mounted by reflow soldering.

Therefore, when multilegged components such as the IC circuit element 7are mounted by reflow soldering after flip-chip mounting of thevibrating elements 20, the support substrate 2 may be curved by thermalstress and thus affect the vibrating elements 20, thereby changing thevibration mode and degrading the characteristics. Also, the supportsubstrate 2 on which the vibrating elements 20 have been mounted ismounted on a control substrate of a main body device by reflowsoldering, the junction between the support substrate 2 and the ICcircuit element 7 may be again reflowed, and thus the vibrating elements20 may be influenced by the curvature of the support substrate 2 or thelike which occurs in the mounting process.

In the above-descried first embodiment, as shown in FIG. 46, the ICcircuit element 7 is mounted near a corner other than the corners of thesupport substrate 2 on which the vibrating elements 20 are mounted. Inaddition, other electronic components are also mounted on a localizedregion of the support substrate 2. Therefore, thermal stress or thermalstrain nonuniformly occurs in the plane of the support substrate 2during reflow, thereby causing nonuniform thermal stress or the like toact on the mounting regions of the pair of the vibrating elements 20.Therefore, a variation may occur between the detection precisions of thevibrating elements.

Accordingly, in this embodiment, as shown in FIG. 47, the main mountingregion of the IC circuit element 7 is located in a central portion of aline which connects the mounting regions of the pair of the vibratingelements 20. As a result, the thermal stress exerted in the reflowprocess of mounting the IC circuit element 7 or the reflow process ofmounting the support substrate 2 on the control substrate may beuniformly distributed to the pair of the vibrating elements 20, and theoccurrence of a difference between the characteristics of the vibratingelements may be suppressed.

As shown in FIG. 47, the mounting region of the IC circuit element ispreferably determined so that the IC circuit element 7 having arectangular planar shape is disposed at a central point (symmetricpoint) between the pair of vibrating elements 20. However, the ICcircuit element 7 may be actually disposed within a predetermined regionwith the mounting region of the IC circuit element 7, which is shown inthe drawing, as a center. The predetermined region means a region inwhich when the plane of the support substrate 2 is divided into first tofourth quadrants, at least a portion of the mounting region of the ICcircuit element 7 belongs to each of the first to fourth quadrants.

As shown in FIG. 47, the mounting regions of the other electroniccomponents 8 as well as the mounting region of the IC circuit element 7are preferably determined to be uniform or symmetric with respect toeach of the vibrating elements 20 so that the respective mountingregions include the same number of the components. As a result, thestress produced in the reflow processes of the other electroniccomponents 8 as well as the IC circuit element 7 may be uniformlyapplied to the vibrating elements 20.

FIG. 48 shows the relation between the number of times of reflow of thesupport substrate 2 and a difference between the outputs of the pair ofthe vibrating elements with changes in the mounting region of the ICcircuit element 7. FIG. 48 indicates that when the difference betweenthe outputs of the vibrating elements is small, the amount of straintransmitted to each vibrating element is uniform, while when thedifference between the outputs is large, the amount of straintransmitted to each vibrating element is large. In this case, the outputdifference before reflow is zero. Also, the embodiment of the inventionshown in FIG. 47 has an obvious effect and causes substantially nodifference between the outputs of the vibrating elements, as comparedwith the structure of a comparative example (FIG. 46) in which the ICcircuit element 7 is localized at a corner of the support substrate 2.

Third Embodiment

Next, a third embodiment of the invention will be described.

FIG. 49 schematically shows a wiring structure between each of thevibrating elements 20 and the corresponding driving detector circuitpart 50 (IC circuit element 7). The reference electrode layer 27 isconnected to the Ref terminal of the driving detector circuit part 50,and the driving electrode layer 29 is connected to the Ga terminal ofthe driving detector circuit part 50. The pair of the detectionelectrodes 30L and 30R are connected to the Gb and Gc terminals,respectively, of the driving detector circuit part 50.

In a usual vibrating gyrosensor, Ref terminal is set at the samepredetermined positive potential as Ga to Gc terminals (for example,1.35 V). Namely, the central potential of an AC signal input to thedriving electrode layer 29 and the central potentials of detectionsignals output from the detection electrodes 30L and 30R are set at thesame as that of the reference electrode layer 27. Therefore, thedetection signals output from the detection electrodes 30L and 30Rindicate values higher and lower (positive and negative) than thereference potential, thereby causing the problem of decreasing thedetection sensitivity with reduction in size of an element.

In the vibrating gyrosensor according to this embodiment, therefore, theRef terminal to which the reference electrode layer 27 is connected isset to the GND (ground) potential. In other words, as shown in FIG. 50,the central potential of the AC signal input to the driving electrodelayer 29 and the central potentials of the detection signals output fromthe detection electrodes 30L and 30R are set to be higher than that ofthe reference electrode layer 27 by a predetermined potential. As aresult, each of the vibrator parts 23 is driven with a predetermined DCbias (offset potential) applied between the Ga to Gc terminals and theRef terminal, and the detection signals output from the detectionelectrodes 30L and 30R are at a potential higher than the referencepotential, thereby increasing the SN ratio and improving the detectionsensitivity.

The magnitude of the offset potential applied between the drivingelectrode layer 29 (detection electrodes 30L and 30R) and the referenceelectrode layer 27 significantly influences the piezoelectric property(output sensitivity) of the piezoelectric thin film layer 28. FIG. 51shows the relation between the offset potential and the piezoelectricproperty. In this figure, the offset potential is represented by thestrength (V/μm) of an electric field acting on the piezoelectric thinfilm layer 28.

FIG. 51 reveals that assuming that the piezoelectric property is 1 whenthe offset potential is 0, the piezoelectric property increases as theoffset potential increases, but tends to decrease when the offsetpotential is about 8 V/μm or more. When the offset potential exceeds 15V/μm, the piezoelectric property decreases to a value lower than that atthe offset potential of 0. Therefore, in this embodiment, the offsetpotential for improving the piezoelectric property is 15 V/μm or lessand preferably 8 V/μm or less.

FIG. 52 shows a hysteresis curve (P-E curve) indicating changes in theamount of polarization with changes in the strength of an externalelectric field of the piezoelectric thin film layer 28. When thereference electrode layer 27 and the driving electrode layer 29 are setat the same potential, the central potential (operating voltage) of aninput signal applied to the driving electrode layer 29 agrees with thecenter (electric strength 0) of the loop shown in FIG. 52. On the otherhand, in this embodiment in which the reference electrode layer 27 isconnected to the GND terminal, the operating voltage is set at aposition shifting to the right side (positive direction of the electricfield strength) from the center of the loop. In this embodiment, theamount of the shift, i.e., the offset potential, is 1.35 V. As a result,the piezoelectric material is driven in a region where the amount ofpolarization is larger than residual polarization Pr of thepiezoelectric material, and accordingly the output voltages of thedetection electrodes 30L and 30R are increased.

Although the piezoelectric material is driven in a region with a largeamount of polarization as the shift amount (offset potential or biaspotential) of the operating voltage increases, the driving direction ofthe piezoelectric material is undesirably suppressed when the amount ofpolarization is close to saturation polarization Ps. Therefore, theshift amount is preferably, for example, the coercive electric field(+Ec) of the piezoelectric material or less.

As descried above, according to this embodiment, the detection voltageis increased to permit the high-sensitivity detection of an angularvelocity or Coriolis' force applied to each vibrator part 23, therebyeasily complying with a reduction in size of the vibrating elements 20,as compared with a general sensor. Also, the operation voltage of eachdriving detector circuit part 50 may be decreased, thereby contributingto the lower power consumption of a vibrating gyrosensor.

As described above, the vibrating gyrosensor descried in thespecification has the following other features:

1. The vibrating gyrosensor including a support substrate on which awiring pattern having a plurality of lands is formed, and a vibratingelement mounted on a surface of the support substrate, wherein thevibrating element includes a base part having a mounting surface onwhich a plurality of terminals to be connected to the lands is formed,and a vibrator part integrally projected from one of the sides of thebase part and having a substrate-facing surface coplanar with themounting surface of the base part, the vibrator part has a firstelectrode layer, a piezoelectric layer, and a second electrode layerwhich are laminated on the substrate-facing surface in that order, andthe vibrator part vibrates when an AC signal is applied between thefirst and second electrode layers, the central electric field strengthof the AC signal being set at a position shifting to the positivedirection from the center of a hysteresis loop of the piezoelectriclayer.

2. The vibrating gyrosensor described in 1, wherein shift amount of thecentral electric field strength of the AC signal is 15 V/μm or less.

3. The vibrating gyrosensor described in 1, wherein the first electrodelayer is connected to a ground potential.

4. The vibrating gyrosensor described in 1, wherein a plurality of thevibrating elements is mounted on the support substrate so that thevibrator parts have different axial directions.

5. The vibrating gyrosensor described in 4, wherein the vibratingelements are driven with an operating frequency difference of 1 kHz ormore.

6. The vibrating gyrosensor described in 4, wherein in addition to theplurality of vibrating elements, a circuit element and a plurality ofelectronic components are mounted on the support substrate.

7. The vibrating gyrosensor described in 6, wherein the circuit elementincludes an IC component, and a main mounting region for the circuitelement is located at a central portion of a line connecting themounting regions of the plurality of vibrating elements.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. A vibrating gyrosensor comprising: a support substrate including afirst surface and a oppositely facing second surface; a wiring patternhaving a plurality of lands on the first surface; and a plurality ofmounting terminal parts on the second surface; and at least twovibrating elements on the first surface of the support substrateeffective to detect vibrations in different axial directions.
 2. Thevibrating gyrosensor according to claim 1, wherein the vibratingelements are driven with an operating frequency difference of 1 kHz ormore.
 3. The vibrating gyrosensor according to claim 2, wherein thevibrating elements are driven with an operating frequency difference of2 kHz to 3 kHz.
 4. The vibrating gyrosensor according to claim 1,wherein at least one of the two vibrating elements is mounted at acorner of the support substrate.
 5. The vibrating gyrosensor accordingto claim 4, wherein the two vibrating elements are mounted at theopposite corners of the support substrate.
 6. The vibrating gyrosensoraccording to claim 1, wherein each of the vibrating elements includes abase part having a mounting surface on which a plurality of terminals tobe connected to the lands is formed, and a vibrator part integrallyprojected in a cantilever manner from one of the sides of the base partand having a substrate-facing surface coplanar with the mounting surfaceof the base part; and the vibrator part has a first electrode layer, apiezoelectric layer, and a second electrode layer, which are formed onthe substrate-facing surface in that order.
 7. The vibrating gyrosensoraccording to claim 6, wherein the two vibrating elements are mounted sothat the vibrator parts are disposed on axes at 90°.
 8. The vibratinggyrosensor according to claim 6, wherein each of the vibrating elementshas metal bumps provided on the plurality of terminal parts formed onthe mounting surface of the base part, and the plurality of terminalparts are connected to the respective lands through the metal bumps. 9.The vibrating gyrosensor according to claim 6, wherein each of thevibrator parts vibrates when an AC signal is applied between the firstelectrode layer and the second electrode layer, and the central electricfield strength of the AC signal is set at a position shifting to thepositive direction from a center of a hysteresis loop of thepiezoelectric layer.
 10. The vibrating gyrosensor according to claim 9,wherein the shift amount of the central electric field strength of theAC signal is 15 V/μm or less.
 11. The vibrating gyrosensor according toclaim 9, wherein the first electrode layer is connected to a groundpotential.
 12. The vibrating gyrosensor according to claim 1, whereinthe vibrator part of each of the vibrating elements has processing marksformed on the tip side thereof, for adjusting its resonance frequency.13. The vibrating gyrosensor according to claim 12, wherein theprocessing marks are formed at a distance of ⅘ of the overall length ofthe vibrator part from the base end thereof.
 14. The vibratinggyrosensor according to claim 1, wherein each of the vibrating elementshas alignment marks for alignment with the support substrate.
 15. Thevibrating gyrosensor according to claim 1, wherein besides the pluralityof vibrating elements, a circuit element and a plurality of electroniccomponents are mounted on the support substrate.
 16. The vibratinggyrosensor according to claim 15, wherein the circuit element includesan IC component, and a mounting region for the circuit element islocated in a central portion of a line connecting the mounting regionsof the plurality of vibrating elements.
 17. The vibrating gyrosensoraccording to claim 1, wherein the surface of the support substrate iscovered with a light-shielding cover member.